_daylight, _dstbias, _timezone, and _tzname
_daylight, _dstbias, _timezone, and _tzname are used in some time and date routines to make local-time adjustments. These global variables have been deprecated in Visual C++ 2005 for the more secure functional versions, which should be used in place of the global variables.
Global variable |
Functional equivalent |
|---|---|
_daylight |
|
_dstbias |
|
_timezone |
|
_tzname |
They are declared in Time.h as follows.
extern int _daylight;
extern int _dstbias;
extern long _timezone;
extern char *_tzname[2];
Comentarios
On a call to _ftime, localtime, or _tzset, the values of _daylight, _dstbias, _timezone, and _tzname are determined from the value of the TZ environment variable. If you do not explicitly set the value of TZ, _tzname[0] and _tzname[1] contain the default settings of "PST" and "PDT" respectively. The time-manipulation functions (_tzset, _ftime, and localtime) attempt to set the values of _daylight, _dstbias and _timezone by querying the operating system for the default value of each variable. The time-zone global variable values are shown in the following table.
Variable |
Value |
|---|---|
_daylight |
Nonzero if daylight saving time (DST) zone is specified in TZ or determined from the operating system; otherwise, 0. The default value is 1. |
_dstbias |
Offset for daylight saving time. |
_timezone |
Difference in seconds between coordinated universal time and local time. The default value is 28,800. |
_tzname[0] |
Time-zone name derived from the TZ environment variable. The default value is "PST". |
_tzname[1] |
DST zone name derived from the TZ environment variable. The default value is "PDT" (Pacific daylight time). |