To support a universal standard, Calendar Server uses the date and time strings in Greenwich Mean Time (GMT) or Coordinated Universal Time (UTC), called Zulu time. The server stores and returns all date and time strings from the database in Zulu time. WCAP converts the Zulu times to the appropriate time zone settings depending upon the value of the tzid and tzidout parameters.
The tzid parameter is used for date and time strings passed in with the dtstart, dtend, and rid parameters, which are not already in Zulu time. WCAP uses the value of the tzid parameter to calculate the Zulu time. If the tzid parameter is not passed in, the server’s default time zone is used to calculate Zulu time.
For commands that return events and todos, the data is returned in Zulu time, unless the tzidout parameter is passed in. In this case the Zulu time is translated into the time zone specified in the tzidout parameter.
For example, if the fetch_components_by range command specifies a date range of 20020506T100000 to 20020507T100000, with a tzid=America/Los_Angeles, WCAP translates that to Zulu time for database lookup. If the tzidout parameter was also passed in (for our example, tzidout=America/New_York), then the resulting output would be translated to that time zone and returned. If the tzidout parameter is missing, the component data is returned in Zulu time.
The tzidout parameter can be used with the storeevents and storetodos command when the fetch parameter is set to 1 (fetch=1).
The time zones information is kept in a plain text file (timezones.ics) in VTIMEZONE format.
The server never uses the system time zone information to calculate the current date and time. It uses the time elapsed in seconds since the Epoch (00:00:00 UTC, January 1, 1970) to calculate current date and time. Then depending on the user’s time zone settings, the date is displayed to reflect the correct time zone.
The following commands use both the tzid and tzidout parameters:
In addition, the following commands use the tzid parameter (but not the tzidout):