From 5578acd4c401246202e95244cf2832e928c4cd5f Mon Sep 17 00:00:00 2001
From: Clockwork <alex@clockwork.gr>
Date: Thu, 30 Nov 2023 08:52:15 +0200
Subject: [PATCH] fix: Ensure RFC dates between years 0001 and 0099 are parsed
 correctly

---
 packages/encoding/src/rfc3339.spec.ts | 21 +++++++++++++++++++++
 packages/encoding/src/rfc3339.ts      |  7 ++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/packages/encoding/src/rfc3339.spec.ts b/packages/encoding/src/rfc3339.spec.ts
index 227f1e32..eef19fc1 100644
--- a/packages/encoding/src/rfc3339.spec.ts
+++ b/packages/encoding/src/rfc3339.spec.ts
@@ -58,6 +58,27 @@ describe("RFC3339", () => {
     expect(fromRfc3339("2002-10-02T11:12:13.999Z")).toEqual(new Date(Date.UTC(2002, 9, 2, 11, 12, 13, 999)));
   });
 
+  it("parses dates between years 0 and 99 with and without timezones", () => {
+    expect(fromRfc3339("0001-01-01T00:00:00.000Z")).toEqual(
+      new Date(new Date(Date.UTC(1, 0, 1, 0, 0, 0, 0)).setUTCFullYear(1)),
+    );
+    expect(fromRfc3339("0000-01-01T00:00:00.000Z")).toEqual(
+      new Date(new Date(Date.UTC(0, 0, 1, 0, 0, 0, 0)).setUTCFullYear(0)),
+    );
+    expect(fromRfc3339("1999-01-01T00:00:00.000Z")).toEqual(
+      new Date(new Date(Date.UTC(1999, 0, 1, 0, 0, 0, 0)).setUTCFullYear(1999)),
+    );
+    expect(fromRfc3339("0099-01-01T00:00:00.000Z")).toEqual(
+      new Date(new Date(Date.UTC(99, 0, 1, 0, 0, 0, 0)).setUTCFullYear(99)),
+    );
+    expect(fromRfc3339("0010-01-01T00:00:00+01:00")).toEqual(
+      new Date(new Date(Date.UTC(9, 11, 31, 23, 0, 0, 0)).setUTCFullYear(9)),
+    );
+    expect(fromRfc3339("0100-01-01T00:00:00+01:00")).toEqual(
+      new Date(new Date(Date.UTC(99, 11, 31, 23, 0, 0, 0)).setUTCFullYear(99)),
+    );
+  });
+
   it("parses dates with low precision fractional seconds", () => {
     // 1 digit
     expect(fromRfc3339("2002-10-02T11:12:13.0Z")).toEqual(new Date(Date.UTC(2002, 9, 2, 11, 12, 13, 0)));
diff --git a/packages/encoding/src/rfc3339.ts b/packages/encoding/src/rfc3339.ts
index a385ca1c..a9165fcd 100644
--- a/packages/encoding/src/rfc3339.ts
+++ b/packages/encoding/src/rfc3339.ts
@@ -40,7 +40,12 @@ export function fromRfc3339(str: string): Date {
 
   const tzOffset = tzOffsetSign * (tzOffsetHours * 60 + tzOffsetMinutes) * 60; // seconds
 
-  const timestamp = Date.UTC(year, month - 1, day, hour, minute, second, milliSeconds) - tzOffset * 1000;
+  let timestamp = Date.UTC(year, month - 1, day, hour, minute, second, milliSeconds);
+
+  // Date.UTC maps year 0-99 to 1900-1999. Ensure the correct year is set and THEN apply the offset
+  const date = new Date(timestamp);
+  timestamp = date.setUTCFullYear(year) - tzOffset * 1000;
+
   return new Date(timestamp);
 }