Unix Timestamp Reference

Notable timestamps, other epochs and how to get the time in code.

Unix time counts the seconds since the Unix epoch, 00:00:00 UTC on 1 January 1970, ignoring leap seconds: every day is exactly 86,400 seconds. Because it's a single number that's the same everywhere at a given moment, it's the standard way to store and compare instants in databases, logs, file systems, JWT claims and APIs.

The year 2038 problem comes from storing Unix time in a signed 32-bit integer, which can count up to 2,147,483,647: 03:14:07 UTC on 19 January 2038. One second later the value wraps around to a negative number that reads as December 1901. Modern 64-bit operating systems, languages and databases use 64-bit time, but embedded devices, old file formats and database columns declared as 32-bit integers can still be affected.

Notable Unix timestamps

Timestamp	Date and time (UTC)	Why it's notable
-2147483648	1901-12-13 20:45:52 UTC	Smallest signed 32-bit timestamp
0	1970-01-01 00:00:00 UTC	The Unix epoch
946684800	2000-01-01 00:00:00 UTC	Start of the year 2000
1000000000	2001-09-09 01:46:40 UTC	Unix time reached one billion
1234567890	2009-02-13 23:31:30 UTC	The famous 1234567890
1500000000	2017-07-14 02:40:00 UTC	1.5 billion seconds
1600000000	2020-09-13 12:26:40 UTC	1.6 billion seconds
1700000000	2023-11-14 22:13:20 UTC	1.7 billion seconds
1800000000	2027-01-15 08:00:00 UTC	1.8 billion seconds
2000000000	2033-05-18 03:33:20 UTC	2 billion seconds
2147483647	2038-01-19 03:14:07 UTC	Largest signed 32-bit timestamp: the year 2038 problem
4294967295	2106-02-07 06:28:15 UTC	Largest unsigned 32-bit timestamp

Other epochs

Systems that count time from a different starting point, and how far it is from the Unix epoch.

System	Epoch	Unit	Offset from Unix
Unix, POSIX, Linux, macOS	1970-01-01 00:00:00 UTC	Seconds	0
JavaScript Date, Java	1970-01-01 00:00:00 UTC	Milliseconds	0 (× 1000)
Windows FILETIME, NTFS	1601-01-01 00:00:00 UTC	100-nanosecond intervals	11644473600 s before Unix
.NET DateTime ticks	0001-01-01 00:00:00	100-nanosecond intervals	62135596800 s before Unix
NTP	1900-01-01 00:00:00 UTC	Seconds	2208988800 s before Unix
GPS time	1980-01-06 00:00:00 UTC	Seconds (no leap seconds)	315964800 s after Unix
Apple Cocoa, Core Data	2001-01-01 00:00:00 UTC	Seconds	978307200 s after Unix
Classic Mac OS, HFS+	1904-01-01 00:00:00	Seconds	2082844800 s before Unix
Excel (Windows default)	Serial day 1 = 1900-01-01	Days	Day 25569 = 1970-01-01

Durations in seconds

Span	Seconds
1 minute	60
1 hour	3,600
1 day	86,400
1 week	604,800
30 days	2,592,000
365 days	31,536,000
366 days (leap year)	31,622,400
Average Gregorian year	31,556,952

Current Unix time in code

Language	Code
JavaScript	Math.floor(Date.now() / 1000)
Python	int(time.time())
Bash	date +%s
Go	time.Now().Unix()
Java	Instant.now().getEpochSecond()
C#	DateTimeOffset.UtcNow.ToUnixTimeSeconds()
PHP	time()
Ruby	Time.now.to_i
Rust	SystemTime::now().duration_since(UNIX_EPOCH)?.as_secs()
PostgreSQL	SELECT extract(epoch FROM now())::bigint;
MySQL	SELECT UNIX_TIMESTAMP();
SQLite	SELECT unixepoch();
Date from timestamp (GNU)	date -u -d @1700000000
Date from timestamp (macOS, BSD)	date -u -r 1700000000

Good to know

Seconds or milliseconds?

A current timestamp in seconds has 10 digits; in milliseconds, 13. JavaScript (Date.now()) and Java (System.currentTimeMillis()) use milliseconds, most other languages and Unix tools use seconds. Mixing them up gives dates in January 1970 or thousands of years ahead.