Date and Time

There are many different ways to storage date and time:

• as a string:

  • easy to read by humans,

  • but hard for computers’ operations, for example to compare dates in a database,

  • many different representations and some times language dependent, e. g.:

    • Wednesday, January 9, 11:13:48 UTC 2019

    • 2018-12-23 08:23:55

    • 23-12-2018 08:23:55 (PT)

    • 12-23-2018 08:23:55 (US)

• as binary represented with numbers or hexadecimal:

  • difficult to read by humans, but easier for computers’ operations.

  • unfortunately, not all software uses the same representation.

How time is counted

Unix time = POSIX time = UNIX Epoch time.

• number of elapsed seconds since 1970-01-01 00:00:00

• Unix, Linux, Firefox, Java, JavaScript, Perl, PHP, Python, Ruby, Tcl, etc

400-year Gregorian calendar cycle.

• number of microseconds since 1601-01-01 00:00:00

• Google Chrome, Windows 32 and 64 bits, NTFS, Cobol, etc