Python in a Nutshell, 2nd Edition

Chapter 12. Time Operations

A Python program can handle time in several ways. Time intervals are floating-point numbers in units of seconds (a fraction of a second is the fractional part of the interval). Particular instants in time are expressed in seconds since a reference instant, known as the epoch. (Midnight, UTC, of January 1, 1970, is a popular epoch used on both Unix and Windows platforms.) Time instants often also need to be expressed as a mixture of units of measurement (e.g., years, months, days, hours, minutes, and seconds), particularly for I/O purposes. I/O, of course, also requires the ability to format times and dates into human-readable strings, and parse them back from string formats.

This chapter covers the time module, which supplies Python’s core time-handling functionality. The time module is somewhat dependent on the underlying system’s C library. The chapter also presents the datetime, sched, and calendar modules from the standard Python library, the third-party modules dateutil and pytz, and some essentials of the popular extension mx.DateTime. mx.DateTime has been around for many years, with behavior across platforms more uniform than time’s, which helps account for its popularity, particularly for date-time representation in database interfaces.