Specifies settings for a time zone.

Syntax

typedef struct _TIME_ZONE_INFORMATION {
  LONG       Bias;
  WCHAR      StandardName[32];
  SYSTEMTIME StandardDate;
  LONG       StandardBias;
  WCHAR      DaylightName[32];
  SYSTEMTIME DaylightDate;
  LONG       DaylightBias;
}TIME_ZONE_INFORMATION, *PTIME_ZONE_INFORMATION;

Members

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 GetTimeZoneInformation 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. For example, "PDT" could indicate Pacific Daylight Time. The string will be returned unchanged by the GetTimeZoneInformation 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.

Remarks

Settings for each time zone are stored in the following registry key:

HKEY_LOCAL_MACHINE
    SOFTWARE
        Microsoft
            Windows NT
                CurrentVersion
                    Time Zones
                        time_zone_name

Each time zone entry includes the following registry values.

typedef struct _REG_TZI_FORMAT
{
    LONG Bias;
    LONG StandardBias;
    LONG DaylightBias;
    SYSTEMTIME StandardDate;
    SYSTEMTIME DaylightDate;
} REG_TZI_FORMAT;

For more information about the Dynamic DST key, see DYNAMIC_TIME_ZONE_INFORMATION.

Examples

For an example, see SetTimeZoneInformation.

Requirements

See Also

DYNAMIC_TIME_ZONE_INFORMATION

GetTimeZoneInformation

SetTimeZoneInformation

SYSTEMTIME

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Build date: 11/19/2009