Given a value returned from time (or any nonnegative integer),
return a time structure corresponding to the local time zone.
localtime (time ())
{
usec = 0
year = 97
mon = 1
mday = 17
sec = 6
zone = CST
min = 15
wday = 1
hour = 1
isdst = 0
yday = 47
}