Calendaring standards

International standards for dates and times

days since the beginning of the Julian Period

system for identifying instants in time; the number of seconds that have elapsed since the UTC midnight before 1 January 1970, ignoring leap seconds

In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.

The Internet Calendaring and Scheduling Core Object Specification (iCalendar) is a media type which allows users to store and exchange calendaring and scheduling information such as events, to-dos, journal entries, and free/busy information, and together with its associated standards has been a cornerstone of the standardization and interoperability of digital calendars across different vendors. Files formatted according to the specification usually have an extension of . With supporting software, such as an email reader or calendar application, recipients of an iCalendar data file can respond

Calendaring Extensions to WebDAV, or CalDAV, is an Internet standard allowing a client to access and manage calendar data along with the ability to schedule meetings with users on the same or on remote servers. It lets multiple users in different locations share, search and synchronize calendar data. It extends the WebDAV (HTTP-based protocol for data manipulation) specification and uses the iCalendar format for the calendar data. The access protocol is defined by . Extensions to CalDAV for scheduling are standardized as . The protocol is used by many important open-source applications.

leap week calendar system in which weeks start on a Monday and the first week of a year starts from the Monday closest to 1 January; e.g. Thu. 31 Dec. 2009 is 2009–W53–4

set of characters used to express date and time

calendar date format

date and time from which a computer measures system time