diff --git a/api/test/window_post.go b/api/test/window_post.go
index dcf6fcebd..874bcadcf 100644
--- a/api/test/window_post.go
+++ b/api/test/window_post.go
@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"github.com/filecoin-project/lotus/api"
+	"github.com/filecoin-project/lotus/build"
+
 	"os"
 	"strings"
 	"testing"
@@ -35,14 +37,14 @@ func TestPledgeSector(t *testing.T, b APIBuilder, blocktime time.Duration, nSect
 	if err := miner.NetConnect(ctx, addrinfo); err != nil {
 		t.Fatal(err)
 	}
-	time.Sleep(time.Second)
+	build.Clock.Sleep(time.Second)
 
 	mine := true
 	done := make(chan struct{})
 	go func() {
 		defer close(done)
 		for mine {
-			time.Sleep(blocktime)
+			build.Clock.Sleep(blocktime)
 			if err := sn[0].MineOne(ctx, func(bool, error) {}); err != nil {
 				t.Error(err)
 			}
@@ -69,7 +71,7 @@ func pledgeSectors(t *testing.T, ctx context.Context, miner TestStorageNode, n i
 			break
 		}
 
-		time.Sleep(100 * time.Millisecond)
+		build.Clock.Sleep(100 * time.Millisecond)
 	}
 
 	fmt.Printf("All sectors is fsm\n")
@@ -94,7 +96,7 @@ func pledgeSectors(t *testing.T, ctx context.Context, miner TestStorageNode, n i
 			}
 		}
 
-		time.Sleep(100 * time.Millisecond)
+		build.Clock.Sleep(100 * time.Millisecond)
 		fmt.Printf("WaitSeal: %d\n", len(s))
 	}
 }
@@ -115,14 +117,14 @@ func TestWindowPost(t *testing.T, b APIBuilder, blocktime time.Duration, nSector
 	if err := miner.NetConnect(ctx, addrinfo); err != nil {
 		t.Fatal(err)
 	}
-	time.Sleep(time.Second)
+	build.Clock.Sleep(time.Second)
 
 	mine := true
 	done := make(chan struct{})
 	go func() {
 		defer close(done)
 		for mine {
-			time.Sleep(blocktime)
+			build.Clock.Sleep(blocktime)
 			if err := sn[0].MineOne(ctx, func(bool, error) {}); err != nil {
 				t.Error(err)
 			}
@@ -150,7 +152,7 @@ func TestWindowPost(t *testing.T, b APIBuilder, blocktime time.Duration, nSector
 		if head.Height()%100 == 0 {
 			fmt.Printf("@%d\n", head.Height())
 		}
-		time.Sleep(blocktime)
+		build.Clock.Sleep(blocktime)
 	}
 
 	p, err := client.StateMinerPower(ctx, maddr, types.EmptyTSK)
diff --git a/build/clock.go b/build/clock.go
new file mode 100644
index 000000000..5b1726720
--- /dev/null
+++ b/build/clock.go
@@ -0,0 +1,10 @@
+package build
+
+import "github.com/raulk/clock"
+
+// Clock is the global clock for the system. In standard builds,
+// we use a real-time clock, which maps to the `time` package.
+//
+// Tests that need control of time can replace this variable with
+// clock.NewMock().
+var Clock = clock.New()
diff --git a/chain/beacon/beacon.go b/chain/beacon/beacon.go
index 2be2e7f1c..7b998c04f 100644
--- a/chain/beacon/beacon.go
+++ b/chain/beacon/beacon.go
@@ -2,12 +2,13 @@ package beacon
 
 import (
 	"context"
-	"time"
 
-	"github.com/filecoin-project/lotus/chain/types"
 	"github.com/filecoin-project/specs-actors/actors/abi"
 	logging "github.com/ipfs/go-log"
 	"golang.org/x/xerrors"
+
+	"github.com/filecoin-project/lotus/build"
+	"github.com/filecoin-project/lotus/chain/types"
 )
 
 var log = logging.Logger("beacon")
@@ -52,7 +53,7 @@ func ValidateBlockValues(b RandomBeacon, h *types.BlockHeader, prevEntry types.B
 }
 
 func BeaconEntriesForBlock(ctx context.Context, beacon RandomBeacon, round abi.ChainEpoch, prev types.BeaconEntry) ([]types.BeaconEntry, error) {
-	start := time.Now()
+	start := build.Clock.Now()
 
 	maxRound := beacon.MaxBeaconRoundForEpoch(round, prev)
 	if maxRound == prev.Round {
@@ -81,7 +82,7 @@ func BeaconEntriesForBlock(ctx context.Context, beacon RandomBeacon, round abi.C
 		}
 	}
 
-	log.Debugw("fetching beacon entries", "took", time.Since(start), "numEntries", len(out))
+	log.Debugw("fetching beacon entries", "took", build.Clock.Since(start), "numEntries", len(out))
 	reverse(out)
 	return out, nil
 }
diff --git a/chain/beacon/drand/drand.go b/chain/beacon/drand/drand.go
index 00ff05f81..1b036bbf0 100644
--- a/chain/beacon/drand/drand.go
+++ b/chain/beacon/drand/drand.go
@@ -21,6 +21,7 @@ import (
 
 	"github.com/filecoin-project/specs-actors/actors/abi"
 
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/beacon"
 	"github.com/filecoin-project/lotus/chain/types"
 	"github.com/filecoin-project/lotus/node/modules/dtypes"
@@ -131,7 +132,7 @@ func (db *DrandBeacon) Entry(ctx context.Context, round uint64) <-chan beacon.Re
 	}
 
 	go func() {
-		start := time.Now()
+		start := build.Clock.Now()
 		log.Infow("start fetching randomness", "round", round)
 		resp, err := db.client.Get(ctx, round)
 
@@ -142,7 +143,7 @@ func (db *DrandBeacon) Entry(ctx context.Context, round uint64) <-chan beacon.Re
 			br.Entry.Round = resp.Round()
 			br.Entry.Data = resp.Signature()
 		}
-		log.Infow("done fetching randomness", "round", round, "took", time.Since(start))
+		log.Infow("done fetching randomness", "round", round, "took", build.Clock.Since(start))
 		out <- br
 		close(out)
 	}()
diff --git a/chain/block_receipt_tracker.go b/chain/block_receipt_tracker.go
index f182fd180..466adef9d 100644
--- a/chain/block_receipt_tracker.go
+++ b/chain/block_receipt_tracker.go
@@ -5,6 +5,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/types"
 	"github.com/hashicorp/golang-lru"
 	peer "github.com/libp2p/go-libp2p-core/peer"
@@ -37,14 +38,14 @@ func (brt *blockReceiptTracker) Add(p peer.ID, ts *types.TipSet) {
 	if !ok {
 		pset := &peerSet{
 			peers: map[peer.ID]time.Time{
-				p: time.Now(),
+				p: build.Clock.Now(),
 			},
 		}
 		brt.cache.Add(ts.Key(), pset)
 		return
 	}
 
-	val.(*peerSet).peers[p] = time.Now()
+	val.(*peerSet).peers[p] = build.Clock.Now()
 }
 
 func (brt *blockReceiptTracker) GetPeers(ts *types.TipSet) []peer.ID {
diff --git a/chain/blocksync/blocksync.go b/chain/blocksync/blocksync.go
index a9251c419..53b9feeff 100644
--- a/chain/blocksync/blocksync.go
+++ b/chain/blocksync/blocksync.go
@@ -11,6 +11,7 @@ import (
 
 	cborutil "github.com/filecoin-project/go-cbor-util"
 
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/store"
 	"github.com/filecoin-project/lotus/chain/types"
 
@@ -126,7 +127,7 @@ func (bss *BlockSyncService) HandleStream(s inet.Stream) {
 	}
 
 	writeDeadline := 60 * time.Second
-	_ = s.SetDeadline(time.Now().Add(writeDeadline))
+	_ = s.SetDeadline(build.Clock.Now().Add(writeDeadline))
 	if err := cborutil.WriteCborRPC(s, resp); err != nil {
 		log.Warnw("failed to write back response for handle stream", "err", err, "peer", s.Conn().RemotePeer())
 		return
diff --git a/chain/blocksync/blocksync_client.go b/chain/blocksync/blocksync_client.go
index daa4b6335..ac8bcc7a1 100644
--- a/chain/blocksync/blocksync_client.go
+++ b/chain/blocksync/blocksync_client.go
@@ -21,6 +21,7 @@ import (
 	"golang.org/x/xerrors"
 
 	cborutil "github.com/filecoin-project/go-cbor-util"
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/store"
 	"github.com/filecoin-project/lotus/chain/types"
 	incrt "github.com/filecoin-project/lotus/lib/increadtimeout"
@@ -91,7 +92,7 @@ func (bs *BlockSync) GetBlocks(ctx context.Context, tsk types.TipSetKey, count i
 	// randomize the first few peers so we don't always pick the same peer
 	shufflePrefix(peers)
 
-	start := time.Now()
+	start := build.Clock.Now()
 	var oerr error
 
 	for _, p := range peers {
@@ -117,7 +118,7 @@ func (bs *BlockSync) GetBlocks(ctx context.Context, tsk types.TipSetKey, count i
 			if err != nil {
 				return nil, xerrors.Errorf("success response from peer failed to process: %w", err)
 			}
-			bs.syncPeers.logGlobalSuccess(time.Since(start))
+			bs.syncPeers.logGlobalSuccess(build.Clock.Since(start))
 			bs.host.ConnManager().TagPeer(p, "bsync", 25)
 			return resp, nil
 		}
@@ -197,7 +198,7 @@ func (bs *BlockSync) GetChainMessages(ctx context.Context, h *types.TipSet, coun
 	}
 
 	var err error
-	start := time.Now()
+	start := build.Clock.Now()
 
 	for _, p := range peers {
 		res, rerr := bs.sendRequestToPeer(ctx, p, req)
@@ -208,7 +209,7 @@ func (bs *BlockSync) GetChainMessages(ctx context.Context, h *types.TipSet, coun
 		}
 
 		if res.Status == StatusOK {
-			bs.syncPeers.logGlobalSuccess(time.Since(start))
+			bs.syncPeers.logGlobalSuccess(build.Clock.Since(start))
 			return res.Chain, nil
 		}
 
@@ -284,17 +285,17 @@ func (bs *BlockSync) fetchBlocksBlockSync(ctx context.Context, p peer.ID, req *B
 	ctx, span := trace.StartSpan(ctx, "blockSyncFetch")
 	defer span.End()
 
-	start := time.Now()
+	start := build.Clock.Now()
 	s, err := bs.host.NewStream(inet.WithNoDial(ctx, "should already have connection"), p, BlockSyncProtocolID)
 	if err != nil {
 		bs.RemovePeer(p)
 		return nil, xerrors.Errorf("failed to open stream to peer: %w", err)
 	}
-	_ = s.SetWriteDeadline(time.Now().Add(5 * time.Second))
+	_ = s.SetWriteDeadline(build.Clock.Now().Add(5 * time.Second))
 
 	if err := cborutil.WriteCborRPC(s, req); err != nil {
 		_ = s.SetWriteDeadline(time.Time{})
-		bs.syncPeers.logFailure(p, time.Since(start))
+		bs.syncPeers.logFailure(p, build.Clock.Since(start))
 		return nil, err
 	}
 	_ = s.SetWriteDeadline(time.Time{})
@@ -302,7 +303,7 @@ func (bs *BlockSync) fetchBlocksBlockSync(ctx context.Context, p peer.ID, req *B
 	var res BlockSyncResponse
 	r := incrt.New(s, 50<<10, 5*time.Second)
 	if err := cborutil.ReadCborRPC(bufio.NewReader(r), &res); err != nil {
-		bs.syncPeers.logFailure(p, time.Since(start))
+		bs.syncPeers.logFailure(p, build.Clock.Since(start))
 		return nil, err
 	}
 
@@ -314,7 +315,7 @@ func (bs *BlockSync) fetchBlocksBlockSync(ctx context.Context, p peer.ID, req *B
 		)
 	}
 
-	bs.syncPeers.logSuccess(p, time.Since(start))
+	bs.syncPeers.logSuccess(p, build.Clock.Since(start))
 	return &res, nil
 }
 
@@ -475,7 +476,7 @@ func (bpt *bsPeerTracker) addPeer(p peer.ID) {
 		return
 	}
 	bpt.peers[p] = &peerStats{
-		firstSeen: time.Now(),
+		firstSeen: build.Clock.Now(),
 	}
 
 }
diff --git a/chain/events/events.go b/chain/events/events.go
index e11507795..4550fc98a 100644
--- a/chain/events/events.go
+++ b/chain/events/events.go
@@ -99,7 +99,7 @@ func (e *Events) listenHeadChanges(ctx context.Context) {
 			log.Warnf("not restarting listenHeadChanges: context error: %s", ctx.Err())
 			return
 		}
-		time.Sleep(time.Second)
+		build.Clock.Sleep(time.Second)
 		log.Info("restarting listenHeadChanges")
 	}
 }
diff --git a/chain/gen/gen.go b/chain/gen/gen.go
index 31d352ed4..3a0ac2187 100644
--- a/chain/gen/gen.go
+++ b/chain/gen/gen.go
@@ -196,7 +196,7 @@ func NewGeneratorWithSectors(numSectors int) (*ChainGen, error) {
 			*genm2,
 		},
 		NetworkName: "",
-		Timestamp:   uint64(time.Now().Add(-500 * time.Duration(build.BlockDelaySecs) * time.Second).Unix()),
+		Timestamp:   uint64(build.Clock.Now().Add(-500 * time.Duration(build.BlockDelaySecs) * time.Second).Unix()),
 	}
 
 	genb, err := genesis2.MakeGenesisBlock(context.TODO(), bs, sys, tpl)
diff --git a/chain/messagepool/messagepool.go b/chain/messagepool/messagepool.go
index b8ac55c59..2939dba13 100644
--- a/chain/messagepool/messagepool.go
+++ b/chain/messagepool/messagepool.go
@@ -23,12 +23,15 @@ import (
 	"golang.org/x/xerrors"
 
 	"github.com/filecoin-project/go-address"
+
 	"github.com/filecoin-project/lotus/api"
 	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/stmgr"
 	"github.com/filecoin-project/lotus/chain/types"
 	"github.com/filecoin-project/lotus/lib/sigs"
 	"github.com/filecoin-project/lotus/node/modules/dtypes"
+
+	"github.com/raulk/clock"
 )
 
 var log = logging.Logger("messagepool")
@@ -66,7 +69,7 @@ type MessagePool struct {
 	lk sync.Mutex
 
 	closer  chan struct{}
-	repubTk *time.Ticker
+	repubTk *clock.Ticker
 
 	localAddrs map[address.Address]struct{}
 
@@ -187,7 +190,7 @@ func New(api Provider, ds dtypes.MetadataDS, netName dtypes.NetworkName) (*Messa
 
 	mp := &MessagePool{
 		closer:        make(chan struct{}),
-		repubTk:       time.NewTicker(time.Duration(build.BlockDelaySecs) * 10 * time.Second),
+		repubTk:       build.Clock.Ticker(time.Duration(build.BlockDelaySecs) * 10 * time.Second),
 		localAddrs:    make(map[address.Address]struct{}),
 		pending:       make(map[address.Address]*msgSet),
 		minGasPrice:   types.NewInt(0),
diff --git a/chain/metrics/consensus.go b/chain/metrics/consensus.go
index bc7e019d2..7d19d5bd6 100644
--- a/chain/metrics/consensus.go
+++ b/chain/metrics/consensus.go
@@ -3,7 +3,6 @@ package metrics
 import (
 	"context"
 	"encoding/json"
-	"time"
 
 	"github.com/filecoin-project/specs-actors/actors/abi"
 	"github.com/ipfs/go-cid"
@@ -11,6 +10,7 @@ import (
 	pubsub "github.com/libp2p/go-libp2p-pubsub"
 	"go.uber.org/fx"
 
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/types"
 	"github.com/filecoin-project/lotus/node/impl/full"
 	"github.com/filecoin-project/lotus/node/modules/helpers"
@@ -89,7 +89,7 @@ func sendHeadNotifs(ctx context.Context, ps *pubsub.PubSub, topic string, chain
 	}
 
 	// using unix nano time makes very sure we pick a nonce higher than previous restart
-	nonce := uint64(time.Now().UnixNano())
+	nonce := uint64(build.Clock.Now().UnixNano())
 
 	for {
 		select {
@@ -107,7 +107,7 @@ func sendHeadNotifs(ctx context.Context, ps *pubsub.PubSub, topic string, chain
 				Height:   n.Val.Height(),
 				Weight:   w,
 				NodeName: nickname,
-				Time:     uint64(time.Now().UnixNano() / 1000_000),
+				Time:     uint64(build.Clock.Now().UnixNano() / 1000_000),
 				Nonce:    nonce,
 			}
 
diff --git a/chain/sub/incoming.go b/chain/sub/incoming.go
index 9dfc2d894..0db132562 100644
--- a/chain/sub/incoming.go
+++ b/chain/sub/incoming.go
@@ -61,7 +61,7 @@ func HandleIncomingBlocks(ctx context.Context, bsub *pubsub.Subscription, s *cha
 		src := msg.GetFrom()
 
 		go func() {
-			start := time.Now()
+			start := build.Clock.Now()
 			log.Debug("about to fetch messages for block from pubsub")
 			bmsgs, err := s.Bsync.FetchMessagesByCids(context.TODO(), blk.BlsMessages)
 			if err != nil {
@@ -75,9 +75,9 @@ func HandleIncomingBlocks(ctx context.Context, bsub *pubsub.Subscription, s *cha
 				return
 			}
 
-			took := time.Since(start)
+			took := build.Clock.Since(start)
 			log.Infow("new block over pubsub", "cid", blk.Header.Cid(), "source", msg.GetFrom(), "msgfetch", took)
-			if delay := time.Now().Unix() - int64(blk.Header.Timestamp); delay > 5 {
+			if delay := build.Clock.Now().Unix() - int64(blk.Header.Timestamp); delay > 5 {
 				log.Warnf("Received block with large delay %d from miner %s", delay, blk.Header.Miner)
 			}
 
@@ -142,9 +142,9 @@ func (bv *BlockValidator) flagPeer(p peer.ID) {
 
 func (bv *BlockValidator) Validate(ctx context.Context, pid peer.ID, msg *pubsub.Message) pubsub.ValidationResult {
 	// track validation time
-	begin := time.Now()
+	begin := build.Clock.Now()
 	defer func() {
-		log.Debugf("block validation time: %s", time.Since(begin))
+		log.Debugf("block validation time: %s", build.Clock.Since(begin))
 	}()
 
 	stats.Record(ctx, metrics.BlockReceived.M(1))
@@ -233,7 +233,7 @@ func (bv *BlockValidator) Validate(ctx context.Context, pid peer.ID, msg *pubsub
 func (bv *BlockValidator) isChainNearSynced() bool {
 	ts := bv.chain.GetHeaviestTipSet()
 	timestamp := ts.MinTimestamp()
-	now := time.Now().UnixNano()
+	now := build.Clock.Now().UnixNano()
 	cutoff := uint64(now) - uint64(6*time.Hour)
 	return timestamp > cutoff
 }
diff --git a/chain/sync.go b/chain/sync.go
index bcfa71267..df067f1e9 100644
--- a/chain/sync.go
+++ b/chain/sync.go
@@ -620,7 +620,7 @@ func (syncer *Syncer) ValidateBlock(ctx context.Context, b *types.FullBlock) (er
 		return nil
 	}
 
-	validationStart := time.Now()
+	validationStart := build.Clock.Now()
 	defer func() {
 		dur := time.Since(validationStart)
 		durMilli := dur.Seconds() * float64(1000)
@@ -665,12 +665,12 @@ func (syncer *Syncer) ValidateBlock(ctx context.Context, b *types.FullBlock) (er
 
 	// fast checks first
 
-	now := uint64(time.Now().Unix())
+	now := uint64(build.Clock.Now().Unix())
 	if h.Timestamp > now+build.AllowableClockDriftSecs {
 		return xerrors.Errorf("block was from the future (now=%d, blk=%d): %w", now, h.Timestamp, ErrTemporal)
 	}
 	if h.Timestamp > now {
-		log.Warn("Got block from the future, but within threshold", h.Timestamp, time.Now().Unix())
+		log.Warn("Got block from the future, but within threshold", h.Timestamp, build.Clock.Now().Unix())
 	}
 
 	if h.Timestamp < baseTs.MinTimestamp()+(build.BlockDelaySecs*uint64(h.Height-baseTs.Height())) {
@@ -1538,6 +1538,6 @@ func (syncer *Syncer) IsEpochBeyondCurrMax(epoch abi.ChainEpoch) bool {
 		return false
 	}
 
-	now := uint64(time.Now().Unix())
+	now := uint64(build.Clock.Now().Unix())
 	return epoch > (abi.ChainEpoch((now-g.Timestamp)/build.BlockDelaySecs) + MaxHeightDrift)
 }
diff --git a/chain/syncstate.go b/chain/syncstate.go
index b213c7483..aaca88303 100644
--- a/chain/syncstate.go
+++ b/chain/syncstate.go
@@ -8,6 +8,7 @@ import (
 	"github.com/filecoin-project/specs-actors/actors/abi"
 
 	"github.com/filecoin-project/lotus/api"
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/types"
 )
 
@@ -48,7 +49,7 @@ func (ss *SyncerState) SetStage(v api.SyncStateStage) {
 	defer ss.lk.Unlock()
 	ss.Stage = v
 	if v == api.StageSyncComplete {
-		ss.End = time.Now()
+		ss.End = build.Clock.Now()
 	}
 }
 
@@ -64,7 +65,7 @@ func (ss *SyncerState) Init(base, target *types.TipSet) {
 	ss.Stage = api.StageHeaders
 	ss.Height = 0
 	ss.Message = ""
-	ss.Start = time.Now()
+	ss.Start = build.Clock.Now()
 	ss.End = time.Time{}
 }
 
@@ -87,7 +88,7 @@ func (ss *SyncerState) Error(err error) {
 	defer ss.lk.Unlock()
 	ss.Message = err.Error()
 	ss.Stage = api.StageSyncErrored
-	ss.End = time.Now()
+	ss.End = build.Clock.Now()
 }
 
 func (ss *SyncerState) Snapshot() SyncerState {
diff --git a/chain/vm/runtime.go b/chain/vm/runtime.go
index 67b1c9d9d..a160e8455 100644
--- a/chain/vm/runtime.go
+++ b/chain/vm/runtime.go
@@ -373,8 +373,7 @@ func (rt *Runtime) Send(to address.Address, method abi.MethodNum, m vmr.CBORMars
 }
 
 func (rt *Runtime) internalSend(from, to address.Address, method abi.MethodNum, value types.BigInt, params []byte) ([]byte, aerrors.ActorError) {
-
-	start := time.Now()
+	start := build.Clock.Now()
 	ctx, span := trace.StartSpan(rt.ctx, "vmc.Send")
 	defer span.End()
 	if span.IsRecordingEvents() {
@@ -528,7 +527,7 @@ func (rt *Runtime) chargeGasInternal(gas GasCharge, skip int) aerrors.ActorError
 	var callers [10]uintptr
 	cout := gruntime.Callers(2+skip, callers[:])
 
-	now := time.Now()
+	now := build.Clock.Now()
 	if rt.lastGasCharge != nil {
 		rt.lastGasCharge.TimeTaken = now.Sub(rt.lastGasChargeTime)
 	}
diff --git a/chain/vm/vm.go b/chain/vm/vm.go
index 2b22fbf10..b46a9236b 100644
--- a/chain/vm/vm.go
+++ b/chain/vm/vm.go
@@ -28,6 +28,7 @@ import (
 	"github.com/filecoin-project/specs-actors/actors/runtime"
 	"github.com/filecoin-project/specs-actors/actors/runtime/exitcode"
 
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/actors/aerrors"
 	"github.com/filecoin-project/lotus/chain/state"
 	"github.com/filecoin-project/lotus/chain/types"
@@ -285,7 +286,7 @@ func checkMessage(msg *types.Message) error {
 }
 
 func (vm *VM) ApplyImplicitMessage(ctx context.Context, msg *types.Message) (*ApplyRet, error) {
-	start := time.Now()
+	start := build.Clock.Now()
 	ret, actorErr, rt := vm.send(ctx, msg, nil, nil, start)
 	rt.finilizeGasTracing()
 	return &ApplyRet{
@@ -302,7 +303,7 @@ func (vm *VM) ApplyImplicitMessage(ctx context.Context, msg *types.Message) (*Ap
 }
 
 func (vm *VM) ApplyMessage(ctx context.Context, cmsg types.ChainMsg) (*ApplyRet, error) {
-	start := time.Now()
+	start := build.Clock.Now()
 	ctx, span := trace.StartSpan(ctx, "vm.ApplyMessage")
 	defer span.End()
 	msg := cmsg.VMMessage()
diff --git a/cli/sync.go b/cli/sync.go
index fbb69a870..57553a068 100644
--- a/cli/sync.go
+++ b/cli/sync.go
@@ -195,7 +195,7 @@ func SyncWait(ctx context.Context, napi api.FullNode) error {
 		case <-ctx.Done():
 			fmt.Println("\nExit by user")
 			return nil
-		case <-time.After(1 * time.Second):
+		case <-build.Clock.After(1 * time.Second):
 		}
 	}
 }
diff --git a/cmd/chain-noise/main.go b/cmd/chain-noise/main.go
index a1e92ee96..4a4a099d8 100644
--- a/cmd/chain-noise/main.go
+++ b/cmd/chain-noise/main.go
@@ -11,6 +11,7 @@ import (
 
 	"github.com/filecoin-project/go-address"
 	"github.com/filecoin-project/lotus/api"
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/types"
 	lcli "github.com/filecoin-project/lotus/cli"
 
@@ -68,7 +69,7 @@ func sendSmallFundsTxs(ctx context.Context, api api.FullNode, from address.Addre
 		sendSet = append(sendSet, naddr)
 	}
 
-	tick := time.NewTicker(time.Second / time.Duration(rate))
+	tick := build.Clock.Ticker(time.Second / time.Duration(rate))
 	for {
 		select {
 		case <-tick.C:
diff --git a/go.mod b/go.mod
index aca92c57f..8a907eb6a 100644
--- a/go.mod
+++ b/go.mod
@@ -103,6 +103,7 @@ require (
 	github.com/multiformats/go-multibase v0.0.3
 	github.com/multiformats/go-multihash v0.0.13
 	github.com/opentracing/opentracing-go v1.1.0
+	github.com/raulk/clock v1.1.0
 	github.com/stretchr/objx v0.2.0 // indirect
 	github.com/stretchr/testify v1.6.1
 	github.com/syndtr/goleveldb v1.0.0
diff --git a/go.sum b/go.sum
index e7e68404e..854069815 100644
--- a/go.sum
+++ b/go.sum
@@ -1221,6 +1221,8 @@ github.com/prometheus/procfs v0.0.11 h1:DhHlBtkHWPYi8O2y31JkK0TF+DGM+51OopZjH/Ia
 github.com/prometheus/procfs v0.0.11/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4OA4YeYWdaU=
 github.com/prometheus/procfs v0.1.0 h1:jhMy6QXfi3y2HEzFoyuCj40z4OZIIHHPtFyCMftmvKA=
 github.com/prometheus/procfs v0.1.0/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4OA4YeYWdaU=
+github.com/raulk/clock v1.1.0 h1:dpb29+UKMbLqiU/jqIJptgLR1nn23HLgMY0sTCDza5Y=
+github.com/raulk/clock v1.1.0/go.mod h1:3MpVxdZ/ODBQDxbN+kzshf5OSZwPjtMDx6BBXBmOeY0=
 github.com/rcrowley/go-metrics v0.0.0-20181016184325-3113b8401b8a/go.mod h1:bCqnVzQkZxMG4s8nGwiZ5l3QUCyqpo9Y+/ZMZ9VjZe4=
 github.com/rogpeppe/fastuuid v0.0.0-20150106093220-6724a57986af/go.mod h1:XWv6SoW27p1b0cqNHllgS5HIMJraePCO15w5zCzIWYg=
 github.com/rogpeppe/fastuuid v1.2.0/go.mod h1:jVj6XXZzXRy/MSR5jhDC/2q6DgLz+nrA6LYCDYWNEvQ=
diff --git a/journal/journal.go b/journal/journal.go
index b664e8fa7..8d509d51c 100644
--- a/journal/journal.go
+++ b/journal/journal.go
@@ -10,6 +10,8 @@ import (
 
 	logging "github.com/ipfs/go-log"
 	"golang.org/x/xerrors"
+
+	"github.com/filecoin-project/lotus/build"
 )
 
 func InitializeSystemJournal(dir string) error {
@@ -103,7 +105,7 @@ func (fsj *fsJournal) rollJournalFile() error {
 		fsj.fi.Close()
 	}
 
-	nfi, err := os.Create(filepath.Join(fsj.journalDir, fmt.Sprintf("lotus-journal-%s.ndjson", time.Now().Format(time.RFC3339))))
+	nfi, err := os.Create(filepath.Join(fsj.journalDir, fmt.Sprintf("lotus-journal-%s.ndjson", build.Clock.Now().Format(time.RFC3339))))
 	if err != nil {
 		return xerrors.Errorf("failed to open journal file: %w", err)
 	}
@@ -130,7 +132,7 @@ func (fsj *fsJournal) runLoop() {
 func (fsj *fsJournal) AddEntry(system string, obj interface{}) {
 	je := &JournalEntry{
 		System:    system,
-		Timestamp: time.Now(),
+		Timestamp: build.Clock.Now(),
 		Val:       obj,
 	}
 	select {
diff --git a/lib/increadtimeout/incrt.go b/lib/increadtimeout/incrt.go
index 0b9c65d4d..dd5a05ff8 100644
--- a/lib/increadtimeout/incrt.go
+++ b/lib/increadtimeout/incrt.go
@@ -5,12 +5,12 @@ import (
 	"time"
 
 	logging "github.com/ipfs/go-log/v2"
+
+	"github.com/filecoin-project/lotus/build"
 )
 
 var log = logging.Logger("incrt")
 
-var now = time.Now
-
 type ReaderDeadline interface {
 	Read([]byte) (int, error)
 	SetReadDeadline(time.Time) error
@@ -45,7 +45,7 @@ func (err errNoWait) Timeout() bool {
 }
 
 func (crt *incrt) Read(buf []byte) (int, error) {
-	start := now()
+	start := build.Clock.Now()
 	if crt.wait == 0 {
 		return 0, errNoWait{}
 	}
@@ -59,7 +59,7 @@ func (crt *incrt) Read(buf []byte) (int, error) {
 
 	_ = crt.rd.SetReadDeadline(time.Time{})
 	if err == nil {
-		dur := now().Sub(start)
+		dur := build.Clock.Now().Sub(start)
 		crt.wait -= dur
 		crt.wait += time.Duration(n) * crt.waitPerByte
 		if crt.wait < 0 {
diff --git a/lib/peermgr/peermgr.go b/lib/peermgr/peermgr.go
index 490f2b229..d275be3d5 100644
--- a/lib/peermgr/peermgr.go
+++ b/lib/peermgr/peermgr.go
@@ -5,6 +5,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/metrics"
 	"github.com/filecoin-project/lotus/node/modules/dtypes"
 	"go.opencensus.io/stats"
@@ -107,7 +108,7 @@ func (pmgr *PeerMgr) Disconnect(p peer.ID) {
 }
 
 func (pmgr *PeerMgr) Run(ctx context.Context) {
-	tick := time.NewTicker(time.Second * 5)
+	tick := build.Clock.Ticker(time.Second * 5)
 	for {
 		select {
 		case <-tick.C:
diff --git a/miner/miner.go b/miner/miner.go
index d81216be2..8c46be675 100644
--- a/miner/miner.go
+++ b/miner/miner.go
@@ -46,7 +46,7 @@ func NewMiner(api api.FullNode, epp gen.WinningPoStProver, addr address.Address)
 		waitFunc: func(ctx context.Context, baseTime uint64) (func(bool, error), error) {
 			// Wait around for half the block time in case other parents come in
 			deadline := baseTime + build.PropagationDelaySecs
-			time.Sleep(time.Until(time.Unix(int64(deadline), 0)))
+			build.Clock.Sleep(build.Clock.Until(time.Unix(int64(deadline), 0)))
 
 			return func(bool, error) {}, nil
 		},
@@ -107,7 +107,7 @@ func (m *Miner) Stop(ctx context.Context) error {
 
 func (m *Miner) niceSleep(d time.Duration) bool {
 	select {
-	case <-time.After(d):
+	case <-build.Clock.After(d):
 		return true
 	case <-m.stop:
 		return false
@@ -170,14 +170,14 @@ func (m *Miner) mine(ctx context.Context) {
 
 		if b != nil {
 			btime := time.Unix(int64(b.Header.Timestamp), 0)
-			if time.Now().Before(btime) {
-				if !m.niceSleep(time.Until(btime)) {
+			if build.Clock.Now().Before(btime) {
+				if !m.niceSleep(build.Clock.Until(btime)) {
 					log.Warnf("received interrupt while waiting to broadcast block, will shutdown after block is sent out")
-					time.Sleep(time.Until(btime))
+					build.Clock.Sleep(build.Clock.Until(btime))
 				}
 			} else {
 				log.Warnw("mined block in the past", "block-time", btime,
-					"time", time.Now(), "duration", time.Since(btime))
+					"time", build.Clock.Now(), "duration", build.Clock.Since(btime))
 			}
 
 			// TODO: should do better 'anti slash' protection here
@@ -201,7 +201,7 @@ func (m *Miner) mine(ctx context.Context) {
 			nextRound := time.Unix(int64(base.TipSet.MinTimestamp()+build.BlockDelaySecs*uint64(base.NullRounds))+int64(build.PropagationDelaySecs), 0)
 
 			select {
-			case <-time.After(time.Until(nextRound)):
+			case <-build.Clock.After(build.Clock.Until(nextRound)):
 			case <-m.stop:
 				stopping := m.stopping
 				m.stop = nil
@@ -271,7 +271,7 @@ func (m *Miner) hasPower(ctx context.Context, addr address.Address, ts *types.Ti
 //  1.
 func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg, error) {
 	log.Debugw("attempting to mine a block", "tipset", types.LogCids(base.TipSet.Cids()))
-	start := time.Now()
+	start := build.Clock.Now()
 
 	round := base.TipSet.Height() + base.NullRounds + 1
 
@@ -283,11 +283,11 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
 		return nil, nil
 	}
 
-	tMBI := time.Now()
+	tMBI := build.Clock.Now()
 
 	beaconPrev := mbi.PrevBeaconEntry
 
-	tDrand := time.Now()
+	tDrand := build.Clock.Now()
 	bvals := mbi.BeaconEntries
 
 	hasPower, err := m.hasPower(ctx, m.address, base.TipSet)
@@ -299,9 +299,9 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
 		return nil, nil
 	}
 
-	tPowercheck := time.Now()
+	tPowercheck := build.Clock.Now()
 
-	log.Infof("Time delta between now and our mining base: %ds (nulls: %d)", uint64(time.Now().Unix())-base.TipSet.MinTimestamp(), base.NullRounds)
+	log.Infof("Time delta between now and our mining base: %ds (nulls: %d)", uint64(build.Clock.Now().Unix())-base.TipSet.MinTimestamp(), base.NullRounds)
 
 	rbase := beaconPrev
 	if len(bvals) > 0 {
@@ -322,7 +322,7 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
 		return nil, nil
 	}
 
-	tTicket := time.Now()
+	tTicket := build.Clock.Now()
 
 	buf := new(bytes.Buffer)
 	if err := m.address.MarshalCBOR(buf); err != nil {
@@ -336,7 +336,7 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
 
 	prand := abi.PoStRandomness(rand)
 
-	tSeed := time.Now()
+	tSeed := build.Clock.Now()
 
 	postProof, err := m.epp.ComputeProof(ctx, mbi.Sectors, prand)
 	if err != nil {
@@ -349,7 +349,7 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
 		return nil, xerrors.Errorf("failed to get pending messages: %w", err)
 	}
 
-	tPending := time.Now()
+	tPending := build.Clock.Now()
 
 	// TODO: winning post proof
 	b, err := m.createBlock(base, m.address, ticket, winner, bvals, postProof, pending)
@@ -357,7 +357,7 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
 		return nil, xerrors.Errorf("failed to create block: %w", err)
 	}
 
-	tCreateBlock := time.Now()
+	tCreateBlock := build.Clock.Now()
 	dur := tCreateBlock.Sub(start)
 	log.Infow("mined new block", "cid", b.Cid(), "height", b.Header.Height, "took", dur)
 	if dur > time.Second*time.Duration(build.BlockDelaySecs) {
@@ -502,7 +502,7 @@ func SelectMessages(ctx context.Context, al ActorLookup, ts *types.TipSet, msgs
 	tooLowFundMsgs := 0
 	tooHighNonceMsgs := 0
 
-	start := time.Now()
+	start := build.Clock.Now()
 	vmValid := time.Duration(0)
 	getbal := time.Duration(0)
 
@@ -511,7 +511,7 @@ func SelectMessages(ctx context.Context, al ActorLookup, ts *types.TipSet, msgs
 	})
 
 	for _, msg := range msgs {
-		vmstart := time.Now()
+		vmstart := build.Clock.Now()
 
 		minGas := vm.PricelistByEpoch(ts.Height()).OnChainMessage(msg.ChainLength()) // TODO: really should be doing just msg.ChainLength() but the sync side of this code doesnt seem to have access to that
 		if err := msg.VMMessage().ValidForBlockInclusion(minGas.Total()); err != nil {
@@ -519,7 +519,7 @@ func SelectMessages(ctx context.Context, al ActorLookup, ts *types.TipSet, msgs
 			continue
 		}
 
-		vmValid += time.Since(vmstart)
+		vmValid += build.Clock.Since(vmstart)
 
 		// TODO: this should be in some more general 'validate message' call
 		if msg.Message.GasLimit > build.BlockGasLimit {
@@ -534,7 +534,7 @@ func SelectMessages(ctx context.Context, al ActorLookup, ts *types.TipSet, msgs
 
 		from := msg.Message.From
 
-		getBalStart := time.Now()
+		getBalStart := build.Clock.Now()
 		if _, ok := inclNonces[from]; !ok {
 			act, err := al(ctx, from, ts.Key())
 			if err != nil {
@@ -545,7 +545,7 @@ func SelectMessages(ctx context.Context, al ActorLookup, ts *types.TipSet, msgs
 			inclNonces[from] = act.Nonce
 			inclBalances[from] = act.Balance
 		}
-		getbal += time.Since(getBalStart)
+		getbal += build.Clock.Since(getBalStart)
 
 		if inclBalances[from].LessThan(msg.Message.RequiredFunds()) {
 			tooLowFundMsgs++
@@ -648,7 +648,7 @@ func SelectMessages(ctx context.Context, al ActorLookup, ts *types.TipSet, msgs
 		log.Warnf("%d messages in mempool had too high nonce", tooHighNonceMsgs)
 	}
 
-	sm := time.Now()
+	sm := build.Clock.Now()
 	if sm.Sub(start) > time.Second {
 		log.Warnw("SelectMessages took a long time",
 			"duration", sm.Sub(start),
diff --git a/node/hello/hello.go b/node/hello/hello.go
index a2a5fbd4e..5f35faafc 100644
--- a/node/hello/hello.go
+++ b/node/hello/hello.go
@@ -15,6 +15,7 @@ import (
 	protocol "github.com/libp2p/go-libp2p-core/protocol"
 
 	cborutil "github.com/filecoin-project/go-cbor-util"
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain"
 	"github.com/filecoin-project/lotus/chain/store"
 	"github.com/filecoin-project/lotus/chain/types"
@@ -67,7 +68,7 @@ func (hs *Service) HandleStream(s inet.Stream) {
 		_ = s.Conn().Close()
 		return
 	}
-	arrived := time.Now()
+	arrived := build.Clock.Now()
 
 	log.Debugw("genesis from hello",
 		"tipset", hmsg.HeaviestTipSet,
@@ -82,7 +83,7 @@ func (hs *Service) HandleStream(s inet.Stream) {
 	go func() {
 		defer s.Close() //nolint:errcheck
 
-		sent := time.Now()
+		sent := build.Clock.Now()
 		msg := &LatencyMessage{
 			TArrial: arrived.UnixNano(),
 			TSent:   sent.UnixNano(),
@@ -99,7 +100,7 @@ func (hs *Service) HandleStream(s inet.Stream) {
 	if len(protos) == 0 {
 		log.Warn("other peer hasnt completed libp2p identify, waiting a bit")
 		// TODO: this better
-		time.Sleep(time.Millisecond * 300)
+		build.Clock.Sleep(time.Millisecond * 300)
 	}
 
 	ts, err := hs.syncer.FetchTipSet(context.Background(), s.Conn().RemotePeer(), types.NewTipSetKey(hmsg.HeaviestTipSet...))
@@ -146,7 +147,7 @@ func (hs *Service) SayHello(ctx context.Context, pid peer.ID) error {
 	}
 	log.Debug("Sending hello message: ", hts.Cids(), hts.Height(), gen.Cid())
 
-	t0 := time.Now()
+	t0 := build.Clock.Now()
 	if err := cborutil.WriteCborRPC(s, hmsg); err != nil {
 		return err
 	}
@@ -155,13 +156,13 @@ func (hs *Service) SayHello(ctx context.Context, pid peer.ID) error {
 		defer s.Close() //nolint:errcheck
 
 		lmsg := &LatencyMessage{}
-		_ = s.SetReadDeadline(time.Now().Add(10 * time.Second))
+		_ = s.SetReadDeadline(build.Clock.Now().Add(10 * time.Second))
 		err := cborutil.ReadCborRPC(s, lmsg)
 		if err != nil {
 			log.Infow("reading latency message", "error", err)
 		}
 
-		t3 := time.Now()
+		t3 := build.Clock.Now()
 		lat := t3.Sub(t0)
 		// add to peer tracker
 		if hs.pmgr != nil {
diff --git a/node/modules/testing/genesis.go b/node/modules/testing/genesis.go
index 930c11fc8..41587ed72 100644
--- a/node/modules/testing/genesis.go
+++ b/node/modules/testing/genesis.go
@@ -7,7 +7,6 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
-	"time"
 
 	"github.com/ipfs/go-blockservice"
 	"github.com/ipfs/go-cid"
@@ -20,6 +19,7 @@ import (
 
 	"github.com/filecoin-project/specs-actors/actors/runtime"
 
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/gen"
 	genesis2 "github.com/filecoin-project/lotus/chain/gen/genesis"
 	"github.com/filecoin-project/lotus/chain/types"
@@ -71,7 +71,7 @@ func MakeGenesis(outFile, genesisTemplate string) func(bs dtypes.ChainBlockstore
 			}
 
 			if template.Timestamp == 0 {
-				template.Timestamp = uint64(time.Now().Unix())
+				template.Timestamp = uint64(build.Clock.Now().Unix())
 			}
 
 			b, err := genesis2.MakeGenesisBlock(context.TODO(), bs, syscalls, template)
diff --git a/storage/miner.go b/storage/miner.go
index a0e2c9225..42a436988 100644
--- a/storage/miner.go
+++ b/storage/miner.go
@@ -167,7 +167,7 @@ func NewWinningPoStProver(api api.FullNode, prover storage.Prover, verifier ffiw
 var _ gen.WinningPoStProver = (*StorageWpp)(nil)
 
 func (wpp *StorageWpp) GenerateCandidates(ctx context.Context, randomness abi.PoStRandomness, eligibleSectorCount uint64) ([]uint64, error) {
-	start := time.Now()
+	start := build.Clock.Now()
 
 	cds, err := wpp.verifier.GenerateWinningPoStSectorChallenge(ctx, wpp.winnRpt, wpp.miner, randomness, eligibleSectorCount)
 	if err != nil {
@@ -185,7 +185,7 @@ func (wpp *StorageWpp) ComputeProof(ctx context.Context, ssi []abi.SectorInfo, r
 
 	log.Infof("Computing WinningPoSt ;%+v; %v", ssi, rand)
 
-	start := time.Now()
+	start := build.Clock.Now()
 	proof, err := wpp.prover.GenerateWinningPoSt(ctx, wpp.miner, ssi, rand)
 	if err != nil {
 		return nil, err
diff --git a/storage/wdpost_run.go b/storage/wdpost_run.go
index f6ec64583..9f3919240 100644
--- a/storage/wdpost_run.go
+++ b/storage/wdpost_run.go
@@ -430,7 +430,7 @@ func (s *WindowPoStScheduler) runPost(ctx context.Context, di miner.DeadlineInfo
 		snums = append(snums, si.SectorNumber)
 	}
 
-	tsStart := time.Now()
+	tsStart := build.Clock.Now()
 
 	log.Infow("generating windowPost",
 		"sectors", len(ssi))
diff --git a/storage/wdpost_sched.go b/storage/wdpost_sched.go
index 077209a4e..8e3221ef9 100644
--- a/storage/wdpost_sched.go
+++ b/storage/wdpost_sched.go
@@ -14,6 +14,7 @@ import (
 	"github.com/filecoin-project/specs-storage/storage"
 
 	"github.com/filecoin-project/lotus/api"
+	"github.com/filecoin-project/lotus/build"
 	"github.com/filecoin-project/lotus/chain/store"
 	"github.com/filecoin-project/lotus/chain/types"
 )
@@ -85,7 +86,7 @@ func (s *WindowPoStScheduler) Run(ctx context.Context) {
 			if err != nil {
 				log.Errorf("ChainNotify error: %+v")
 
-				time.Sleep(10 * time.Second)
+				build.Clock.Sleep(10 * time.Second)
 				continue
 			}
 
diff --git a/tools/stats/metrics.go b/tools/stats/metrics.go
index 626363731..3abb4b13b 100644
--- a/tools/stats/metrics.go
+++ b/tools/stats/metrics.go
@@ -66,7 +66,7 @@ func NewInfluxWriteQueue(ctx context.Context, influx client.Client) *InfluxWrite
 				for i := 0; i < maxRetries; i++ {
 					if err := influx.Write(batch); err != nil {
 						log.Warnw("Failed to write batch", "error", err)
-						time.Sleep(time.Second * 15)
+						build.Clock.Sleep(15 * time.Second)
 						continue
 					}
 
@@ -104,7 +104,7 @@ func InfluxNewBatch() (client.BatchPoints, error) {
 }
 
 func NewPoint(name string, value interface{}) models.Point {
-	pt, _ := models.NewPoint(name, models.Tags{}, map[string]interface{}{"value": value}, time.Now())
+	pt, _ := models.NewPoint(name, models.Tags{}, map[string]interface{}{"value": value}, build.Clock.Now())
 	return pt
 }
 
diff --git a/tools/stats/rpc.go b/tools/stats/rpc.go
index d053ff561..6b6cef283 100644
--- a/tools/stats/rpc.go
+++ b/tools/stats/rpc.go
@@ -52,7 +52,7 @@ sync_complete:
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
-		case <-time.After(5 * time.Second):
+		case <-build.Clock.After(5 * time.Second):
 			state, err := napi.SyncState(ctx)
 			if err != nil {
 				return err
@@ -97,13 +97,13 @@ sync_complete:
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
-		case <-time.After(5 * time.Second):
+		case <-build.Clock.After(5 * time.Second):
 			head, err := napi.ChainHead(ctx)
 			if err != nil {
 				return err
 			}
 
-			timestampDelta := time.Now().Unix() - int64(head.MinTimestamp())
+			timestampDelta := build.Clock.Now().Unix() - int64(head.MinTimestamp())
 
 			log.Infow(
 				"Waiting for reasonable head height",