From 7f80f9fb8f6d9d363c6b20929c6899d592bf734d Mon Sep 17 00:00:00 2001
From: Guy Bedford <guybedford@gmail.com>
Date: Fri, 9 Oct 2026 19:48:12 -0700
Subject: [PATCH] fs: preserve negative utimes timestamps

`toUnixTimestamp()` silently replaced negative numeric timestamps with
the current time, while negative strings and Dates were passed through
as pre-epoch times.

On Windows, stat times were additionally reinterpreted as unsigned so
that pre-epoch times read back as post-2038 times. Treat negative times
as pre-epoch on all platforms, consistent with POSIX, at the cost of
post-2038 times on Windows which libuv is unable to represent.

Fixes: https://github.com/nodejs/node/issues/64597
Refs: https://github.com/nodejs/node/pull/64627
Assisted-by: OpenCode
Signed-off-by: Guy Bedford <guybedford@gmail.com>
---
 doc/api/fs.md                         |  9 ++++--
 lib/internal/fs/utils.js              |  4 ---
 src/node_file-inl.h                   | 10 -------
 test/parallel/test-fs-utimes-y2K38.js | 43 +++++++++++----------------
 test/parallel/test-fs-utimes.js       | 40 +++++++++++--------------
 5 files changed, 43 insertions(+), 63 deletions(-)

diff --git a/doc/api/fs.md b/doc/api/fs.md
index d6eb4208ef0a..b8b2b9363875 100644
--- a/doc/api/fs.md
+++ b/doc/api/fs.md
@@ -2229,7 +2229,8 @@ Change the file system timestamps of the object referenced by `path`.
 The `atime` and `mtime` arguments follow these rules:
 
 * Values can be either numbers representing Unix epoch time, `Date`s, or a
-  numeric string like `'123456789.0'`.
+  numeric string like `'123456789.0'`. Negative values represent times before
+  the Unix epoch.
 * If the value can not be converted to a number, or is `NaN`, `Infinity`, or
   `-Infinity`, an `Error` will be thrown.
 
@@ -5316,7 +5317,8 @@ Change the file system timestamps of the object referenced by `path`.
 The `atime` and `mtime` arguments follow these rules:
 
 * Values can be either numbers representing Unix epoch time in seconds,
-  `Date`s, or a numeric string like `'123456789.0'`.
+  `Date`s, or a numeric string like `'123456789.0'`. Negative values represent
+  times before the Unix epoch.
 * If the value can not be converted to a number, or is `NaN`, `Infinity`, or
   `-Infinity`, an `Error` will be thrown.
 
@@ -8250,6 +8252,9 @@ The times in the stat object have the following semantics:
 Prior to Node.js 0.12, the `ctime` held the `birthtime` on Windows systems. As
 of 0.12, `ctime` is not "creation time", and on Unix systems, it never was.
 
+On Windows, times are limited to the range of a signed 32-bit number of seconds
+from the Unix epoch, so times after `2038-01-19T03:14:07Z` are not supported.
+
 ### Class: `fs.StatFs`
 
 <!-- YAML
diff --git a/lib/internal/fs/utils.js b/lib/internal/fs/utils.js
index 3aadc19c4732..01f1fe2c214f 100644
--- a/lib/internal/fs/utils.js
+++ b/lib/internal/fs/utils.js
@@ -5,7 +5,6 @@ const {
   ArrayPrototypePush,
   BigInt,
   Date,
-  DateNow,
   DatePrototypeGetTime,
   ErrorCaptureStackTrace,
   FunctionPrototypeCall,
@@ -867,9 +866,6 @@ function toUnixTimestamp(time, name = 'time') {
     return +time;
   }
   if (NumberIsFinite(time)) {
-    if (time < 0) {
-      return DateNow() / 1000;
-    }
     return time;
   }
   if (isDate(time)) {
diff --git a/src/node_file-inl.h b/src/node_file-inl.h
index 803446b1efba..751fa07ef0f5 100644
--- a/src/node_file-inl.h
+++ b/src/node_file-inl.h
@@ -101,18 +101,8 @@ void FillStatsArray(AliasedBufferBase<NativeT, V8T>* fields,
   fields->SetValue(offset + static_cast<size_t>(FsStatsOffset::stat_offset),   \
                    static_cast<NativeT>(stat))
 
-// On win32, time is stored in uint64_t and starts from 1601-01-01.
-// libuv calculates tv_sec and tv_nsec from it and converts to signed long,
-// which causes Y2038 overflow. On the other platforms it is safe to treat
-// negative values as pre-epoch time.
-#ifdef _WIN32
-#define SET_FIELD_WITH_TIME_STAT(stat_offset, stat)                            \
-  /* NOLINTNEXTLINE(runtime/int) */                                            \
-  SET_FIELD_WITH_STAT(stat_offset, static_cast<unsigned long>(stat))
-#else
 #define SET_FIELD_WITH_TIME_STAT(stat_offset, stat)                            \
   SET_FIELD_WITH_STAT(stat_offset, static_cast<double>(stat))
-#endif  // _WIN32
 
   SET_FIELD_WITH_STAT(kDev, s->st_dev);
   SET_FIELD_WITH_STAT(kMode, s->st_mode);
diff --git a/test/parallel/test-fs-utimes-y2K38.js b/test/parallel/test-fs-utimes-y2K38.js
index 9e42e90feb1f..2a12a3f512f8 100644
--- a/test/parallel/test-fs-utimes-y2K38.js
+++ b/test/parallel/test-fs-utimes-y2K38.js
@@ -7,9 +7,24 @@ tmpdir.refresh();
 const assert = require('assert');
 const fs = require('fs');
 
-// Check for Y2K38 support. For Windows, assume it's there. Windows
-// doesn't have `touch` and `date -r` which are used in the check for support.
-if (!common.isWindows) {
+// Ref: https://github.com/nodejs/node/issues/13255
+const path = `${tmpdir.path}/test-utimes-precision`;
+fs.writeFileSync(path, '');
+
+if (common.isWindows) {
+  // This value would get converted to (double)1713037251359.9998
+  const truncate_mtime = 1713037251360;
+  fs.utimesSync(path, truncate_mtime / 1000, truncate_mtime / 1000);
+  const truncate_stats = fs.statSync(path);
+  assert.strictEqual(truncate_stats.mtime.getTime(), truncate_mtime);
+
+  // Libuv stores Windows timestamps in a 32-bit `long tv_sec`, so Y2K38
+  // times can not be represented. Negative values are pre-epoch times.
+  common.skip('Y2K38 is not supported on Windows');
+}
+
+// Check for Y2K38 support.
+{
   const testFilePath = `${tmpdir.path}/y2k38-test`;
   const testFileDate = '204001020304';
   const { spawnSync } = require('child_process');
@@ -38,29 +53,7 @@ if (!common.isWindows) {
   }
 }
 
-// Ref: https://github.com/nodejs/node/issues/13255
-const path = `${tmpdir.path}/test-utimes-precision`;
-fs.writeFileSync(path, '');
-
 const Y2K38_mtime = 2 ** 31;
 fs.utimesSync(path, Y2K38_mtime, Y2K38_mtime);
 const Y2K38_stats = fs.statSync(path);
 assert.strictEqual(Y2K38_stats.mtime.getTime() / 1000, Y2K38_mtime);
-
-if (common.isWindows) {
-  // This value would get converted to (double)1713037251359.9998
-  const truncate_mtime = 1713037251360;
-  fs.utimesSync(path, truncate_mtime / 1000, truncate_mtime / 1000);
-  const truncate_stats = fs.statSync(path);
-  assert.strictEqual(truncate_stats.mtime.getTime(), truncate_mtime);
-
-  // test Y2K38 for windows
-  // This value if treaded as a `signed long` gets converted to -2135622133469.
-  // POSIX systems stores timestamps in {long t_sec, long t_usec}.
-  // NTFS stores times in nanoseconds in a single `uint64_t`, so when libuv
-  // calculates (long)`uv_timespec_t.tv_sec` we get 2's complement.
-  const overflow_mtime = 2159345162531;
-  fs.utimesSync(path, overflow_mtime / 1000, overflow_mtime / 1000);
-  const overflow_stats = fs.statSync(path);
-  assert.strictEqual(overflow_stats.mtime.getTime(), overflow_mtime);
-}
diff --git a/test/parallel/test-fs-utimes.js b/test/parallel/test-fs-utimes.js
index fc11c0791ddb..5b465ba71853 100644
--- a/test/parallel/test-fs-utimes.js
+++ b/test/parallel/test-fs-utimes.js
@@ -45,11 +45,13 @@ function stat_resource(resource, statSync = fs.statSync) {
   return fs.fstatSync(resource);
 }
 
+function toSeconds(time) {
+  return typeof time === 'object' ? time.getTime() / 1000 : +time;
+}
+
 function check_mtime(resource, mtime, statSync) {
-  mtime = fs._toUnixTimestamp(mtime);
   const stats = stat_resource(resource, statSync);
-  const real_mtime = fs._toUnixTimestamp(stats.mtime);
-  return mtime - real_mtime;
+  return toSeconds(mtime) - toSeconds(stats.mtime);
 }
 
 function expect_errno(syscall, resource, err, errno) {
@@ -64,17 +66,12 @@ function expect_ok(syscall, resource, err, atime, mtime, statSync) {
   assert(
     // Check up to single-second precision.
     // Sub-second precision is OS and fs dependent.
-    !err && (mtime_diff < 2) || err && err.code === 'ENOSYS',
+    !err && (Math.abs(mtime_diff) < 2) || err && err.code === 'ENOSYS',
     `FAILED: expect_ok ${util.inspect(arguments)}
      check_mtime: ${mtime_diff}`
   );
 }
 
-function getExpectedMtime(mtime) {
-  // Negative numeric timestamps are normalized to "now" at call time.
-  return fs._toUnixTimestamp(mtime);
-}
-
 const stats = fs.statSync(tmpdir.path);
 
 const asPath = (path) => path;
@@ -85,7 +82,12 @@ const cases = [
   [asPath, new Date()],
   [asPath, 123456.789],
   [asPath, stats.mtime],
-  [asPath, '123456', -1],
+  // AIX rejects pre-epoch timestamps with EINVAL.
+  ...(common.isAIX ? [] : [
+    [asPath, '123456', -1],
+    [asPath, -1234567890],
+    [asPath, new Date('1969-07-20T20:17:40Z')],
+  ]),
   [asPath, new Date('2017-04-08T17:59:38.008Z')],
   [asUrl, new Date()],
 ];
@@ -103,13 +105,11 @@ function runTests(iter) {
   //
   // test async code paths
   //
-  const expectedUtimesMtime = getExpectedMtime(mtime);
   fs.utimes(pathType(tmpdir.path), atime, mtime, common.mustCall((err) => {
-    expect_ok('utimes', tmpdir.path, err, atime, expectedUtimesMtime);
+    expect_ok('utimes', tmpdir.path, err, atime, mtime);
 
-    const expectedLutimesMtime = getExpectedMtime(mtime);
     fs.lutimes(pathType(lpath), atime, mtime, common.mustCall((err) => {
-      expect_ok('lutimes', lpath, err, atime, expectedLutimesMtime, fs.lstatSync);
+      expect_ok('lutimes', lpath, err, atime, mtime, fs.lstatSync);
 
       fs.utimes(pathType('foobarbaz'), atime, mtime, common.mustCall((err) => {
         expect_errno('utimes', 'foobarbaz', err, 'ENOENT');
@@ -121,9 +121,8 @@ function runTests(iter) {
           fd = fs.openSync(tmpdir.path, 'r');
         }
 
-        const expectedFutimesMtime = getExpectedMtime(mtime);
         fs.futimes(fd, atime, mtime, common.mustCall((err) => {
-          expect_ok('futimes', fd, err, atime, expectedFutimesMtime);
+          expect_ok('futimes', fd, err, atime, mtime);
 
           syncTests();
 
@@ -137,20 +136,17 @@ function runTests(iter) {
   // test synchronized code paths, these functions throw on failure
   //
   function syncTests() {
-    const expectedUtimesMtime = getExpectedMtime(mtime);
     fs.utimesSync(pathType(tmpdir.path), atime, mtime);
-    expect_ok('utimesSync', tmpdir.path, undefined, atime, expectedUtimesMtime);
+    expect_ok('utimesSync', tmpdir.path, undefined, atime, mtime);
 
-    const expectedLutimesMtime = getExpectedMtime(mtime);
     fs.lutimesSync(pathType(lpath), atime, mtime);
-    expect_ok('lutimesSync', lpath, undefined, atime, expectedLutimesMtime, fs.lstatSync);
+    expect_ok('lutimesSync', lpath, undefined, atime, mtime, fs.lstatSync);
 
     // Some systems don't have futimes
     // if there's an error, it should be ENOSYS
     try {
-      const expectedFutimesMtime = getExpectedMtime(mtime);
       fs.futimesSync(fd, atime, mtime);
-      expect_ok('futimesSync', fd, undefined, atime, expectedFutimesMtime);
+      expect_ok('futimesSync', fd, undefined, atime, mtime);
     } catch (ex) {
       expect_errno('futimesSync', fd, ex, 'ENOSYS');
     }