mktime
Defined in header
<time.h>
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Renormalizes local calendar time expressed as a struct tm object and also converts it to time since epoch as a time_t object. time->tm_wday
and time->tm_yday
are ignored. The values in time
are not checked for being out of range.
A negative value of time->tm_isdst
causes mktime
to attempt to determine if Daylight Saving Time was in effect in the specified time.
If the conversion to time_t
is successful, the time
object is modified. All fields of time
are updated to fit their proper ranges. time->tm_wday
and time->tm_yday
are recalculated using information available in other fields.
Contents |
[edit] Parameters
time | - | pointer to a tm object specifying local calendar time to convert |
[edit] Return value
time since epoch as a time_t object on success or -1 if time
cannot be represented as a time_t object (POSIX also requires EOVERFLOW
to be stored in errno in this case).
[edit] Notes
If the struct tm object was obtained from POSIX strptime or equivalent function, the value of tm_isdst
is indeterminate, and needs to be set explicitly before calling mktime
.
[edit] Example
Output:
Today is Tue Feb 17 13:46:01 2015 100 months ago was Tue Oct 17 14:46:01 2006
[edit] References
- C11 standard (ISO/IEC 9899:2011):
-
- 7.27.2.3 The mktime function (p: 390-391)
- C99 standard (ISO/IEC 9899:1999):
-
- 7.23.2.3 The mktime function (p: 340-341)
- C89/C90 standard (ISO/IEC 9899:1990):
-
- 4.12.2.3 The mktime function
[edit] See also
(C11)
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converts time since epoch to calendar time expressed as local time (function) |
C++ documentation for mktime
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