Close #14180: Factorize code to convert a number of seconds to time_t, timeval or timespec time.ctime(), gmtime(), time.localtime(), datetime.date.fromtimestamp(), datetime.datetime.fromtimestamp() and datetime.datetime.utcfromtimestamp() now raises an OverflowError, instead of a ValueError, if the timestamp does not fit in time_t. datetime.datetime.fromtimestamp() and datetime.datetime.utcfromtimestamp() now round microseconds towards zero instead of rounding to nearest with ties going away from zero.