These functions perform calendrical computations using time values
(see Time of Day). A value of
nil for any of their
time-value arguments stands for the current system time, and a single
integer number stands for the number of seconds since the epoch.
This returns the time difference t1 − t2 between two time values, as a time value. If you need the difference in units of elapsed seconds, use
float-time(see float-time) to convert the result into seconds.
This returns the sum of two time values, as a time value. One argument should represent a time difference rather than a point in time, either as a list or as a single number of elapsed seconds. Here is how to add a number of seconds to a time value:(time-add time seconds)
This function returns the number of days between the beginning of year 1 and time-value.
This returns the day number within the year corresponding to time-value.