Calendar

A calendar is a means of determining and organising the passage of time, particularly for social, religious and administrative purposes. Periods of time, such as weeks, months and years are noted, with a particular date being a specific day within these periods.

In universe
Different races and cultures have devised calendars to meet their particular circumstances.
 * Human calendars
 * Gregorian calendar
 * Indian National calendar
 * Julian calendar
 * Mayan calendar
 * Risan calendar
 * Tandaran calendar
 * Vomnin calendar
 * Vulcan calendar

Real world
Various Star Trek calendars have been published over the years, tying in to the television shows, characters and starships.
 * Ships of the Line calendars
 * Star Trek Ships
 * Star Trek: Deep Space Nine calendar