@node Timefns@chapter Time Functions (@file{time.h})This chapter groups functions used either for reporting on time(elapsed, current, or compute time) or to perform calculations basedon time.The header file @file{time.h} defines three types.  @code{clock_t} and@code{time_t} are both used for representations of time particularlysuitable for arithmetic.  (In this implementation, quantities of type@code{clock_t} have the highest resolution possible on your machine,and quantities of type @code{time_t} resolve to seconds.)  @code{size_t}is also defined if necessary for quantities representing sizes. @file{time.h} also defines the structure @code{tm} for the traditionalrepresentation of Gregorian calendar time as a series of numbers, withthe following fields: @table @code@item tm_secSeconds.@item tm_minMinutes.@item tm_hourHours.@item tm_mdayDay.@item tm_monMonth.@item tm_yearYear (since 1900).@item tm_wdayDay of week: the number of days since Sunday.@item tm_ydayNumber of days elapsed since last January 1.@item tm_isdstDaylight Savings Time flag: positive means DST in effect, zero means DSTnot in effect, negative means no information about DST is available.@end table@menu* asctime::     Format time as string* clock::       Cumulative processor time* ctime::       Convert time to local and format as string* difftime::    Subtract two times* gmtime::      Convert time to UTC (GMT) traditional representation* localtime::   Convert time to local representation* mktime::      Convert time to arithmetic representation* strftime::    Flexible calendar time formatter* time::        Get current calendar time (as single number)* tzset::       Set timezone info@end menu@page@include time/asctime.def@page@include time/clock.def@page@include time/ctime.def@page@include time/difftime.def@page@include time/gmtime.def@page@include time/lcltime.def@page@include time/mktime.def@page@include time/strftime.def@page@include time/time.def@page@include time/tzset.def