Ctime converts a time clock such as returned by time(2) into ASCII
(sic) and returns a pointer to a 30–byte string in the following
form. All the fields have constant width.
Localtime and gmtime return pointers to structures containing
the broken–down time. Localtime corrects for the time zone and
possible daylight savings time; gmtime converts directly to GMT.
Asctime converts a broken–down time to ASCII and returns a pointer
to a 30–byte string.
Wed Aug 5 01:07:47 EST 1973\n\0
Tm2sec converts a broken–down time to seconds since the start of
the epoch. It ignores wday, and assumes the local time zone if
zone is not GMT.
When local time is first requested, the program consults the timezone
environment variable to determine the time zone and converts accordingly.
(This variable is set at system boot time by init(8).) The timezone
variable contains the normal time zone name and its difference
from GMT in seconds followed by an
alternate (daylight) time zone name and its difference followed
by a newline. The remainder is a list of pairs of times (seconds
past the start of 1970, in the first time zone) when the alternate
time zone applies. For example:
int sec; /* seconds (range 0..59) */|
int min; /* minutes (0..59) */
int hour; /* hours (0..23) */
int mday; /* day of the month (1..31) */
int mon; /* month of the year (0..11) */
int year; /* year A.D. – 1900 */
int wday; /* day of week (0..6, Sunday = 0) */
int yday; /* day of year (0..365) */
char zone; /* time zone name */
int tzoff; /* time zone delta from GMT */
Greenwich Mean Time is represented by
EST –18000 EDT –14400|
9943200 25664400 41392800 57718800 ...|