Time zone conversion overview

This document describes the Symbian platform time zone conversion component.

About time zones and daylight saving time

Time zones

Time zones are regions that have adopted the same standard time. All time zones are defined relative to UTC (Coordinated Universal Time) which is the international time standard. See http://www.ghcc.msfc.nasa.gov/utc.html for more details.

The time for a location is given relative to UTC. For example:
  • Mumbai, India: UTC + 5:30 (For example, if it is 12:00 UTC, then it is 17:30 in Mumbai)

  • Tokyo, Japan: UTC + 9 (For example, if it is 12:00 UTC, then it is 21:00 in Tokyo)

Note: The local time may need to be adjusted due to the use of a daylight saving time offset.

The list of time zones used within a country are found in Time zone list. Select a country to view all the time zones used within that country. The time zones follow a "Location/Area" format, with "Location" being a continent or geographic region of the world and "Area" being a time zone region within that location, for example, "Europe/Vienna".

Local time

The local time is the time according to the local time zone (the place where the phone user is physically located). The local time is sometimes referred to as "wall clock" time.

If local time is 10:00 hours in the US Eastern time zone, then the local time in the US Pacific time zone is 07:00 hours. This is because US Eastern Time is 4 hours behind UTC (UTC -4) and US Pacific Time is 7 hours behind UTC (UTC –7 ).

If a phone user’s normal location is in the US Eastern time zone, and travels to a location in the US Pacific time zone, the phone time zone should be changed to US Pacific Time.

The system time zone is the time zone to which the device is set.

Time zone conversion

The time zone component allows you to set the system time zone and to convert time between UTC and any time, past, present or future, for any time zone, as long as a rule exists for the conversion. The change rules include when to change to and from daylight saving time for each time zone.

The time zone rules are provided in a Symbian-native database which is created from Olson’s TZ database. It can be configured by device manufacturers to save space. The time zone rules for the current time zone are cached by the time zone server so that they are quicker to access for future conversions.

Using the time zone component you can do the following:

  • configure the current local time zone.

  • convert a UTC time to the local time for the system time zone.

  • convert a UTC time to the local time for a time zone provided by the user.

  • convert the local time for the system time zone to UTC.

  • convert the local time for any time zone provided by the user to UTC.

The key classes involved are CTzId, RTz and CTzConverter.

Figure: Class diagram for Time zone Conversion

See also