fs: incorrect handling of numeric times from before the unix epoch

[johnp]

Version

v22.16.0

Platform

Linux johnp-pc 7.1.3-200.fc44.x86_64 #1 SMP PREEMPT_DYNAMIC Sat Jul  4 19:20:12 UTC 2026 x86_64 GNU/Linux

Subsystem

node:fs

What steps will reproduce the bug?

Description

Since 1f842c2, NodeJS internally modifies numeric negative utimes to the current time. This is unexpected, as negative strings ("-1") work as expected. This issue was previously reported, but not all possible types (date, string, number) were considered. and the bug therefore wrongly closed.

Reproducer

import fs from 'node:fs';

const file = 'neg_timespec.txt';
fs.writeFileSync(file, 'test');

// Set time to -1 second before 1970
fs.utimesSync(file, -1, -1);

const stats = fs.statSync(file);
console.log("Expected mtime (ms): -1000");
console.log("Actual mtime (ms):  ", stats.mtime.getTime());

fs.unlinkSync(file);

Incorrect code

node/lib/internal/fs/utils.js

Lines 783 to 793 in 4f844f4

	function toUnixTimestamp(time, name = 'time') {
	// eslint-disable-next-line eqeqeq
	if (typeof time === 'string' && +time == time) {
	return +time;
	}
	if (NumberIsFinite(time)) {
	if (time < 0) {
	return DateNow() / 1000;
	}
	return time;
	}

How often does it reproduce? Is there a required condition?

100%

What is the expected behavior? Why is that the expected behavior?

Expected mtime (ms): -1500

What do you see instead?

Actual mtime (ms): 1784465433024

Additional information

Found investigating the Rust port of Bun, where the bug was copied by AI presumably.