Changing ZCS Time Zones

 - This article is a Work in Progress, and may be unfinished or missing sections.

Time zones change when governments change daylight saving time policies. When a time zone changes, it is necessary to change the time zone settings in ZCS. This article discusses the tools and steps used to change time zone settings in a deployed Zimbra Collaboration Suite server.

To read more about how ZCS interacts with time zones, see Time Zones in ZCS.

ZCS Time Zone Tools

The following tools are used to define and change time zone settings in ZCS.

timezones.ics

The timezones.ics file contains a list of well-known time zones. This file is a valid iCalendar (RFC2445) object containing a VTIMEZONE block for each time zone. It is located in /opt/zimbra/conf/.

The basic client and other JSP-based clients must know an account's default time zone to render the Calendar view. Calendar resource accounts (e.g. conference rooms) must have a default time zone set to auto-accept/decline meetings. These default time zones must be chosen from the time zones defined in the timezones.ics file.

To change a time zone, you must locate and edit its VTIMEZONE definition. Changes to the timezone.ics file become effective when the mailboxd process is restarted.

The following section identifies each part of the VTIMEZONE definitions.

VTIMEZONE Definitions

Each timezone listed in the timezone.ics file is described using a VTIMEZONE definition. The following example is the VTIMEZONE definition for US Pacific Time.

BEGIN:VTIMEZONE
TZID:(GMT-08.00) Pacific Time (US & Canada)
LAST-MODIFIED:20070209T005655Z
BEGIN:STANDARD
DTSTART:16010101T020000
TZOFFSETTO:-0800
TZOFFSETFROM:-0700
RRULE:FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTH=11;BYDAY=1SU
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:16010101T020000
TZOFFSETTO:-0700
TZOFFSETFROM:-0800
RRULE:FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTH=3;BYDAY=2SU
END:DAYLIGHT
END:VTIMEZONE

This definition is composed of a series of properties describing US Pacific Time. The following table lists the properties of a VTIMEZONE definition.

Note: The properties below are described based on their use in ZCS. For more information about the iCalendar syntax, refer to RFC2445.

VTIMEZONE Properties
Name	Description
BEGIN <VTIMEZONE>	This defines the beginning of a VTIMEZONE definition.
END <VTIMEZONE>	This defines the end of a VTIMEZONE definition.
TZID	This is the name of the time zone being defined. Important: This element should not be modified.
LAST-MODIFIED	This is a time stamp indicating when the time zone definition was last modified. While this is not currently used, it is recommended that you update the time stamp when you modify the definition. The date and time is given in the form of <YYYYMMDD>T<hhmmss>Z. For example, the LAST-MODIFIED value for a definition that was modified October 5th, 2008 at 2:41 pm would be 20081005T144100Z.
BEGIN <STANDARD|DAYLIGHT>	This defines the beginning of either a standard time or daylight savings time rule set. A time zone that uses daylight savings time will have two BEGIN entries, one defining standard time and the other defining daylight savings time. A time zone that doesn't use daylight savings time will only have one BEGIN entry defining standard time.
END <STANDARD|DAYLIGHT>	This defines the end of either a standard time or daylight savings time rule set.
DTSTART	This defines the date and time the standard or daylight time rule set is applied. The date is not important, as long as it is set for a prior date. The default date for ZCS time zones is 16010101. The time indicates in local time when to apply standard or daylight savings time. The date and time is given in the form of <YYYYMMDD>T<hhmmss>. For example, a daylight savings time DTSTART value of 160101T020000 indicates that any transition to daylight savings time occurring after Jan. 1st, 1601 should be applied at 2:00 am local time. Note: This value should be set, even if the time zone does not use daylight savings time.
TZOFFSETTO	This indicates the GMT offset after the transition. If the time zone does not use daylight savings time, the TZOFFSETTO value and the TZOFFSETFROM value are both the year-round GMT offset of the time zone. The offset is given in the form of +/-hhmm. For example, -0800.
TZOFFSETFROM	This indicates the GMT offset before the transition. If the time zone does not use daylight savings time, the TZOFFSETTO value and the TZOFFSETFROM value are both the year-round GMT offset of the time zone. The offset is given in the form of +/-hhmm. For examples, -0700.
RRULE	This specifies the rule for the transition date. Month value ranges from 1 to 12, 1 being January. Week value is a week number followed by a 2-letter weekday. Week number ranges from 1 to 4, or can be -1 for the last week of the month. Weekday values are SU, MO, TU, WE, TH, FR, and SA. For example, US Pacific Standard Time is set to BYMONTH=11;BYDAY=1SU, indicating the transition to standard time happens on the first Sunday of November. Important: Settings for FREQ, WKST, and INTERVAL should not be changed. Note: If the time zone does not use daylight savings time, the RRULE is not specified.

Examples

• In this example, we have changed US Pacific Time to start daylight savings time on the first Wednesday of April at 5:00 am and to transition to standard time on the last Saturday of October at 6:30 am.

BEGIN:VTIMEZONE
TZID:(GMT-08.00) Pacific Time (US & Canada)
LAST-MODIFIED:20070209T005655Z
BEGIN:STANDARD
DTSTART:16010101T063000
TZOFFSETTO:-0800
TZOFFSETFROM:-0700
RRULE:FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTH=10;BYDAY=-1SA
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:16010101T050000
TZOFFSETTO:-0800
TZOFFSETFROM:-0700
RRULE:FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTH=4;BYDAY=1WE
END:DAYLIGHT
END:VTIMEZONE

• In this example, we have changed US Pacific Time to no longer use daylight savings time.

BEGIN:VTIMEZONE
TZID:(GMT-08.00) Pacific Time (US & Canada)
LAST-MODIFIED:20070209T005655Z
BEGIN:STANDARD
DTSTART:16010101T020000
TZOFFSETTO:-0800
TZOFFSETFROM:-0700
END:STANDARD
END:VTIMEZONE

Note: Because daylight savings time is not being used, the RRULE property is not used in this definition.

Changing a ZCS Time Zone Setting

Use the following instructions to change a time zone setting on a ZCS server.

1. In the timezones.ics file, make the necessary changes to the relevant VTIMEZONE entry.

2. Restart Zimbra Services.

zmcontrol stop
zmcontrol start

3. Using zmtzupdate, update existing appointments with the changed time zone settings.