ctime.3c (2010 09)

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ctime(3C) ctime(3C)

gmtime() Convert directly to Coordinated Universal Time (UTC), the time standard used by the

HP-UX operating system. gmtime() returns a pointer to the

tm structure

described below.

The minimum date supported by

gmtime() in both 32-bit and 64-bit HP-UX is Fri-

day December 13 20:45:52 UTC 1901. The maximum dates supported by

gmtime()

are Tuesday January 19 03:14:07 UTC 2038 and Friday December 31 23:59:59 UTC

9999 in 32-bit HP-UX and 64-bit HP-UX, respectively.

In 64-bit HP-UX,

gmtime() returns NULL and sets errno to [ERANGE] if timer is

less than the number of seconds that corresponds to the minimum date supported

(i.e., INT_MIN, as deﬁned in

limits.h), or exceeds the number of seconds that

corresponds to the maximum date supported.

gmtime_r() is identical to gmtime(), except that

gmtime_r() stores the result in the tm

struct pointed to by result and returns

result upon success.

localtime() Correct for the time zone and any summer time zone adjustments (such as Daylight

Savings Time in the USA), according to the contents of the

TZ environment variable

(see Environment Variables below).

localtime() returns a pointer to the tm

structure described below.

The minimum date supported by

localtime() in both 32-bit and 64-bit HP-UX is

Friday December 13 20:45:52 UTC 1901. The maximum dates supported by

local-

time()

are Tuesday January 19 03:14:07 UTC 2038 and Friday December 31

23:59:59 UTC 9999 in 32-bit HP-UX and 64-bit HP-UX, respectively.

In 64-bit HP-UX,

localtime() returns NULL and sets errno to [ERANGE] if timer

is less than the number of seconds that corresponds to the minimum date supported

(i.e., INT_MIN, as deﬁned in limits.h), or exceeds the number of seconds that

corresponds to the maximum date supported.

localtime_r() is identical to

localtime(), except that localtime_r() stores the result in the

tm struct pointed to by result and returns result upon success.

mktime() Convert the broken-down time (expressed as local time) in the structure pointed to by

timeptr into a calendar time value with the same encoding as that of the values

returned by time(). The original values of the tm_wday and tm_yday com-

ponents of the structure are ignored, and the original values of the other components

are not restricted to the ranges indicated below.

A positive or zero value for

tm_isdst causes mktime() to initially presume that

Daylight Saving Time respectively is or is not in effect for the speciﬁed time. A nega-

tive value for tm_isdst causes mktime() to attempt to determine whether Day-

light Saving Time is in effect for the speciﬁed time.

Upon successful completion, all the components are set to represent the speciﬁed

calendar time, but with their values forced to the ranges indicated below. The ﬁnal

value of

tm_mday is not set until tm_mon and tm_year are determined.

mktime() returns the speciﬁed calendar time encoded as a value of type time_t.

The minimum date supported by

mktime() in both 32-bit and 64-bit HP-UX is Fri-

day December 13 20:45:52 UTC 1901. The maximum dates supported by mktime()

are Tuesday January 19 03:14:07 UTC 2038 and Friday December 31 23:59:59 UTC

9999 in 32-bit HP-UX and 64-bit HP-UX, respectively.

For 32-bit

mktime(), if the calendar time cannot be represented, the function

returns the value (time_t) — 1 and sets errno to [ERANGE]. Note the value

(time_t) — 1 also corresponds to the time 23:59:59 on Dec 31, 1969 (plus or minus

time zone and Daylight Saving Time adjustments). Thus it is necessary to check both

the return value and errno to reliably detect an error condition.

The behavior of 64-bit

mktime() beyond the supported ranges is undeﬁned.

tzset() Sets the values of the external variables timezone , daylight , and tzname according to

the contents of the TZ environment variable (independent of any time value). The

functions localtime(), mktime(), ctime(), asctime(), and strftime()

(see strftime (3C)) call tzset() and use the values returned in the external vari-

ables described below for their operations. tzset() can also be called directly by

2 Hewlett-Packard Company − 2 − HP-UX 11i Version 3: September 2010