Set a time using date-to-time
(date-to-time "May 20 2011 19:30:00") => (19926 45864)
Note that the date strings format is dependent on your machine’s locale settings. For example, the following may be necessary. For more about locales, read this post.
(date-to-time "20 May 2011 19:30:00")
Enter a date using parse-time-string
(setq concert (parse-time-string "May 20 2011 19:30:00")) => (0 30 19 20 5 2011 nil nil nil)
Unlike date-to-time, parse-time-string allows you to omit the time value :
(setq birthday (parse-time-string "July 29 1953")) => (nil nil nil 29 7 1953 nil nil nil)
Here are some times:
(setq five-seconds (seconds-to-time 5))
(setq ninety-minutes (seconds-to-time (* 60 90)))
(setq one-day (seconds-to-time (* 60 60 24)))
The last can be more easily entered as:
(setq one-day (days-to-time 1))
Which leads to
(setq one-week (days-to-time 7))
and so on…