Starlight Tools

Mac HFS+ Timestamp Converter - HFS Plus Seconds Since 1904

Convert a Mac timestamp, HFS Plus timestamp, HFS+ timestamp, or Mac OS Extended timestamp to a readable date. HFS+ values are whole seconds since January 1, 1904 GMT/UTC, and every conversion runs locally in your browser.

HFS+ Timestamp to Date

Current Mac HFS+ timestamp
...
Live seconds since 1904-01-01T00:00:00Z.
Paste a decimal integer, 0x hex value, compact hex, or spaced hex bytes.
Auto-detect keeps decimal values decimal and treats spaced byte strings as big-endian.

Date to HFS+ Timestamp

Interpreted in your current local time zone.
ISO-8601 offsets are respected.

Display Settings

Results always include UTC; this controls the extra local view.
Unix <-> HFS+ offset: 2,082,844,800 seconds.

Batch Decode HFS+ Values

About HFS+ Time

HFS+, also known as HFS Plus or Mac OS Extended, stores file-system timestamps as whole seconds since 1904-01-01T00:00:00Z. Compared with Unix time, the exact epoch gap is 2,082,844,800 seconds.

  • HFS+ to Unix seconds: unix = hfs - 2,082,844,800
  • Unix seconds to HFS+: hfs = unix + 2,082,844,800
  • Endianness: HFS Plus on-disk structures are big-endian; little-endian previews help when raw bytes were copied in reverse order.
  • Range: an unsigned 32-bit HFS+ timestamp spans 1904-01-01T00:00:00Z through 2040-02-06T06:28:15Z. The often-cited 2106 date is Unix unsigned 32-bit overflow, not HFS+ unsigned 32-bit overflow.

HFS+ Time Code Examples

Compact examples for converting between HFS+ seconds since 1904-01-01 UTC and human time. Example input 2082844800 decodes to 1970-01-01T00:00:00Z.

const HFS_OFFSET = 2082844800n;
function hfsToDate(hfs) {
  return new Date(Number((BigInt(hfs) - HFS_OFFSET) * 1000n));
}
function dateToHfs(date) {
  return BigInt(Math.floor(date.getTime() / 1000)) + HFS_OFFSET;
}
console.log(hfsToDate(2082844800n).toISOString()); // 1970-01-01T00:00:00.000Z

Known HFS+ Timestamp Values

Value Meaning UTC date
0Start of the HFS+ epoch1904-01-01T00:00:00Z
2082844800Unix epoch offset in decimal1970-01-01T00:00:00Z
0x7C25B080Unix epoch offset in hexadecimal1970-01-01T00:00:00Z
4294967295Maximum unsigned 32-bit HFS+ timestamp2040-02-06T06:28:15Z
4294967296Next second wraps to 0 in unsigned 32-bit fields1904-01-01T00:00:00Z after wrap

HFS+ Timestamp FAQ

What is a Mac HFS+ timestamp?

A Mac HFS+ timestamp, also called an HFS Plus timestamp or Mac OS Extended timestamp, counts whole seconds since January 1, 1904 at 00:00:00 GMT/UTC.

Is Mac timestamp the same as Cocoa/Core Data time?

No. HFS+ time starts at 1904-01-01 UTC. Cocoa and Core Data absolute time start at 2001-01-01 UTC, so the numeric values are different even when they describe the same instant.

Does HFS+ use UTC or local time?

HFS Plus timestamps are defined as seconds from the 1904 epoch in GMT/UTC. This tool decodes to UTC first and then shows the selected local time zone for convenience.

Why does HFS+ start in 1904?

The classic Mac epoch starts at 1904-01-01, which begins a leap-year cycle and avoids the special 1900 leap-year rule that complicates calendar arithmetic.

What happens in 2040?

An unsigned 32-bit HFS+ field reaches 4294967295 at 2040-02-06T06:28:15Z. If a field is limited to 32 bits, the next second wraps to 0, which represents 1904-01-01T00:00:00Z.

How do I convert HFS+ to Unix time?

Subtract 2,082,844,800 from the HFS+ timestamp. Add the same offset to convert Unix seconds back to HFS+ seconds.

Is HFS+ big-endian?

Yes. HFS Plus volume structures are big-endian on disk. If you have copied four raw bytes from a little-endian view, use the little-endian input mode or compare the swapped-byte preview.

Which file metadata fields use HFS+ timestamps?

HFS Plus catalog records use timestamp fields for metadata such as creation time, content modification time, attribute modification time, access time, and backup time.

References and Accuracy Notes

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