timeZone is a virtual class and has no slots.

The splusTimeDate package contains built-in time zones for the 24 standard time zones around the world. We also include daylight savings time in various areas, and standard time for Central Australia, which is 1/2 hour off Eastern Australia. Currently, the correct daylight savings areas provided are:

• US (1967 and beyond).
• Canada (1974 and beyond).
• New Zealand (1976 and beyond).
• Australia (1973 and beyond).
• Great Britain (1972 and beyond).
• European Union (1977 and beyond).
• Hong Kong (1970 and beyond).

Also, we provide a special time zone for Singapore, which was 7:30 ahead of GMT until May of 1982, when it changed over to 8:00.

The official names of the time zones, in order around the world, are shown below along with their offset from Universal Coordinated Time (UTC, also known as GMT).

You can use the time zones listed in Built-In Zones for various operations on timeDate objects, including reading times from character data, writing times as character data, and converting between time zones. However, normally the names listed in the table are not used directly, because users want to use the names commonly used in their areas, such as CST for Central Standard Time in the US, Canada, or Australia. The correspondence between "convenient" and "official" names is set up using the timeZoneList function.

Besides using the time zones listed in Built-In Zones, users can also define their own time zones through use of the timeZoneR class. This class allows specification of a time zone with an offset from GMT, in seconds, in the offset slot, and a data frame containing rules for when and how to go on daylight savings time in the rules slot. (If there is no daylight savings time in this time zone, the data frame should be empty or have 0 rows.)

Each row in the rules data frame encodes a range of years' daylight savings rules; they must be in order to work properly. The rules are encoded in the following columns of the data frame (which must be in order, and all of class integer):

yearfrom	starting year for rules, or -1 to start at the beginning of time.
yearto	ending year for rules, or -1 to end at the end of time.
hasdaylight	indicates whether daylight savings time is used in this year range. Note that this is an integer value, 1 or 0, for true or false.
dsextra	offset (in seconds) to add to the regular offset when daylight time is in effect.
monthstart	month (1-12) in which daylight savings time starts (may be before monthend for southern hemisphere).
codestart	code telling how to interpret daystart and xdaystart to calculate the day within the month for starting daylight savings time.
	1 = start on the daystart (1-31) day of the month.
	2 = start on the last daystart (0-Sunday through 6-Saturday) weekday in the month.
	3 = start on the first daystart weekday (0-Sunday through 6-Saturday) on or after the xdaystart (1-31) day of the month.
	4 = start on the last daystart weekday (0-Sunday through 6-Saturday) on or before the xdaystart (1-31) day of the month.
daystart	see codestart.
xdaystart	see codestart.
timestart	seconds after midnight local standard time to start daylight savings time, on the day specified by codestart, and so on.
monthend	month (1-12) in which daylight savings time ends (may be after monthstart for southern hemisphere).
codeend	code telling how to interpret dayend and xdayend to calculate the day within the month for ending daylight savings time.
	1 = end on the dayend (1-31) day of the month.
	2 = end on the last dayend (0-Sunday through 6-Saturday) weekday in the month.
	3 = end on the first dayend weekday (0-Sunday through 6-Saturday) on or after the xdayend (1-31) day of the month.
	4 = end on the last dayend weekday (0-Sunday through 6-Saturday) on or before the xdayend (1-31) day of the month.
dayend	see codeend.
xdayend	see codeend. For examples, see the timeZoneR function. To use user-defined time zones, you must put them in the time zone list (see timeZoneList function).
timeend	seconds after midnight local standard time to end daylight savings time, on the day specified by codeend, etc.

Daylight savings boundaries and other time zone information was taken from the public-domain time zone library from the ftp://elsie.nci.nih.gov/pub/ ftp site.