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

No. HFS+ time counts seconds since 1904-01-01 UTC. Cocoa and Core Data absolute time count seconds since 2001-01-01 UTC.

Yes. HFS Plus volume structures are stored big-endian on disk. Little-endian byte strings are common when bytes were copied from another tool or read in reverse order.

What happens to HFS+ timestamps in 2040?

An unsigned 32-bit HFS+ timestamp reaches 4,294,967,295 at 2040-02-06T06:28:15Z. The next second wraps to 0 in fields limited to 32 bits.

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.

HFS+ seconds, hex, or raw bytes

Paste a decimal integer, 0x hex value, compact hex, or spaced hex bytes.

Input mode

Auto-detect keeps decimal values decimal and treats spaced byte strings as big-endian.

Forensic interpretations

Interpretation	Decimal HFS+	Hex	UTC date

The swapped-byte preview is shown for 4-byte values so copied disk bytes can be compared as big-endian and little-endian quickly.

Date to HFS+ Timestamp

Local date and time

Interpreted in your current local time zone.

Or paste a date/time string

ISO-8601 offsets are respected.

Include hex Show as unsigned 32-bit

Display Settings

Display time zone

Results always include UTC; this controls the extra local view.

Unix <-> HFS+ offset: 2,082,844,800 seconds.

Batch Decode HFS+ Values

Paste multiple timestamps or byte strings

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

import datetime
HFS_OFFSET = 2_082_844_800
def hfs_to_datetime(hfs: int) -> datetime.datetime:
    return datetime.datetime.fromtimestamp(hfs - HFS_OFFSET, datetime.timezone.utc)
def datetime_to_hfs(dt: datetime.datetime) -> int:
    return int(dt.timestamp()) + HFS_OFFSET
print(hfs_to_datetime(2082844800).isoformat())  # 1970-01-01T00:00:00+00:00

let hfsOffset: TimeInterval = 2_082_844_800
func hfsToDate(_ hfs: TimeInterval) -> Date {
    Date(timeIntervalSince1970: hfs - hfsOffset)
}
func dateToHfs(_ date: Date) -> TimeInterval {
    date.timeIntervalSince1970 + hfsOffset
}
print(ISO8601DateFormatter().string(from: hfsToDate(2_082_844_800))) // 1970-01-01T00:00:00Z

#include <stdint.h>
#define HFS_OFFSET 2082844800LL
int64_t hfs_to_unix(uint32_t hfs) {
    return (int64_t)hfs - HFS_OFFSET;
}
uint32_t unix_to_hfs(int64_t unix_seconds) {
    return (uint32_t)(unix_seconds + HFS_OFFSET);
}
/* hfs_to_unix(2082844800u) == 0, or 1970-01-01T00:00:00Z */

Known HFS+ Timestamp Values

Value	Meaning	UTC date
`0`	Start of the HFS+ epoch	`1904-01-01T00:00:00Z`
`2082844800`	Unix epoch offset in decimal	`1970-01-01T00:00:00Z`
`0x7C25B080`	Unix epoch offset in hexadecimal	`1970-01-01T00:00:00Z`
`4294967295`	Maximum unsigned 32-bit HFS+ timestamp	`2040-02-06T06:28:15Z`
`4294967296`	Next second wraps to `0` in unsigned 32-bit fields	`1904-01-01T00:00:00Z` 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

Apple Technical Note TN1150: HFS Plus Volume Format for the HFS Plus epoch, catalog fields, and big-endian volume structures.
Epoch Converter Mac HFS+ timestamp converter for current Mac timestamp comparison.
Digital Detective DCode for forensic timestamp decoding workflows and endian-oriented input examples.
File-system date-range reference for the HFS/HFS Plus range ending at 2040-02-06 06:28:15 UTC for 32-bit timestamp fields.