Time - (Unix|POSIX|Epoch) time

1 - About

Unix time (also known as POSIX time or Epoch time) is a system for describing instants in time.

It is used widely in Unix-like and many other operating systems and file formats.

3 - Precision

3.1 - Second

It's the number of seconds (or millisecond) that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970, not counting leap seconds.

Because it does not handle leap seconds, it is neither a linear representation of time nor a true representation of UTC.


  • after the epoch have positive values,
  • before the epoch have negative values.

3.2 - Day

An epoch day is a incrementing count of days where day 0 is 1970-01-01.

4 - Command

4.1 - Bash / Linux

Unix time may be checked on most Unix systems by typing date +%s on the command line.

4.2 - Java


4.3 - Oracle

  • Example 1:

myDate = TO_DATE('19700101000000','YYYYMMDDHH24MISS') + NUMTODSINTERVAL(myUnixTimeStamp, 'SECOND')

  • Example 2:

select TO_CHAR( FROM_TZ( CAST(DATE '1970-01-01' + (1/24/60/60/1000) * <column name> AS TIMESTAMP), 'America/New_York'), 'MM/DD/YYYY HH24:MI:SS') from <tablename>;

5 - Documentation / Reference

Data Science
Data Analysis
Data Science
Linear Algebra Mathematics

Powered by ComboStrap