Specifies settings for a time zone and dynamic daylight saving time.
- Bias
The current bias for local time translation on this computer, in minutes. The bias is the difference, in
minutes, between Coordinated Universal Time (UTC) and local time. All translations between UTC and local time
are based on the following formula:
UTC = local time + bias
This member is required.
- StandardName
A description for standard time. For example, "EST" could indicate Eastern Standard Time. The string will
be returned unchanged by the
GetDynamicTimeZoneInformation
function. This string can be empty.
- StandardDate
A SYSTEMTIME structure that contains a date and
local time when the transition from daylight saving time to standard time occurs on this operating system. If
the time zone does not support daylight saving time or if the caller needs to disable daylight saving time, the
wMonth member in the
SYSTEMTIME structure must be zero. If this date is
specified, the DaylightDate member of this structure must also be specified.
Otherwise, the system assumes the time zone data is invalid and no changes will be applied.
To select the correct day in the month, set the wYear member to zero, the
wHour and wMinute members to the transition time, the
wDayOfWeek member to the appropriate weekday, and the
wDay member to indicate the occurrence of the day of the week within the month (1 to
5, where 5 indicates the final occurrence during the month if that day of the week does not occur 5 times).
Using this notation, specify 02:00 on the first Sunday in April as follows:
wHour = 2, wMonth = 4,
wDayOfWeek = 0, wDay = 1. Specify 02:00 on the last
Thursday in October as follows: wHour = 2, wMonth = 10,
wDayOfWeek = 4, wDay = 5.
If the
wYear member is not zero, the transition date is absolute; it will only occur one
time. Otherwise, it is a relative date that occurs yearly.
- StandardBias
The bias value to be used during local time translations that occur during standard time. This member is
ignored if a value for the StandardDate member is not supplied.
This value is added to the value of the Bias member to form the bias used during
standard time. In most time zones, the value of this member is zero.
- DaylightName
A description for daylight saving time (DST). For example, "PDT" could indicate Pacific Daylight Time. The
string will be returned unchanged by the
GetDynamicTimeZoneInformation
function. This string can be empty.
- DaylightDate
A SYSTEMTIME structure that contains a
date and local time when the transition from standard time to daylight saving time occurs on this operating
system. If the time zone does not support daylight saving time or if the caller needs to disable daylight
saving time, the wMonth member in the
SYSTEMTIME structure must be zero. If this date is
specified, the StandardDate member in this structure must also be specified.
Otherwise, the system assumes the time zone data is invalid and no changes will be applied.
To select the correct day in the month, set the wYear member to zero, the
wHour and wMinute members to the transition time, the
wDayOfWeek member to the appropriate weekday, and the
wDay member to indicate the occurrence of the day of the week within the month (1 to
5, where 5 indicates the final occurrence during the month if that day of the week does not occur 5 times).
If the wYear member is not zero, the transition date is absolute; it will only
occur one time. Otherwise, it is a relative date that occurs yearly.
- DaylightBias
The bias value to be used during local time translations that occur during daylight saving time. This member
is ignored if a value for the DaylightDate member is not supplied.
This value is added to the value of the Bias member to form the bias used during
daylight saving time. In most time zones, the value of this member is –60.
- TimeZoneKeyName
The name of the time zone registry key on the local computer. For more information, see Remarks.
- DynamicDaylightTimeDisabled
Indicates whether dynamic daylight saving time is disabled. Setting this member to TRUE disables dynamic
daylight saving time, causing the system to use a fixed set of transition dates.
To restore dynamic daylight saving time, call the
SetDynamicTimeZoneInformation
function with DynamicDaylightTimeDisabled set to FALSE.
The system will read the transition dates for the current year at the next time update, the next system reboot,
or the end of the calendar year (whichever comes first.)
When calling the
GetDynamicTimeZoneInformation
function, this member is TRUE if the time zone was set using the
SetTimeZoneInformation function instead of
SetDynamicTimeZoneInformation or if
the user has disabled this feature using the Date and Time application in Control
Panel.
To disable daylight saving time, set this member to TRUE, clear the
StandardDate and DaylightDate members, and call
SetDynamicTimeZoneInformation. To
restore daylight saving time, call
SetDynamicTimeZoneInformation with
DynamicDaylightTimeDisabled set to FALSE.
Dynamic daylight saving time provides support for time zones whose boundaries for daylight saving time change
from year to year. This feature enables easier updating of systems, especially for locales where the yearly DST
boundaries are known in advance. After the time zone has been updated, the current time zone setting is applied to
all time operations, even when the time in question occurred before the time zone changed. Therefore, it is best
to store UTC times and convert them to the current local time zone.