New Features for Dealing with Times And Time Delays

• The new function current-time returns the system's time value as a list of three integers: (high low microsec). The integers high and low combine to give the number of seconds since 0:00 January 1, 1970, which is high * 2**16 + low. microsec gives the microseconds since the start of the current second (or 0 for systems that return time only on the resolution of a second).
• The function current-time-string accepts an optional argument time-value. If given, this specifies a time to format instead of the current time. The argument should be a cons cell containing two integers, or a list whose first two elements are integers. Thus, you can use times obtained from current-time (see above) and from file-attributes.
• You can now find out the user's time zone using current-time-zone. The value has the form (OFFSET name). Here offset is an integer giving the number of seconds ahead of UTC (east of Greenwich). A negative value means west of Greenwich. The second element, name is a string giving the name of the time zone. Both elements change when daylight savings time begins or ends; if the user has specified a time zone that does not use a seasonal time adjustment, then the value is constant through time. If the operating system doesn't supply all the information necessary to compute the value, both elements of the list are nil. The optional argument time-value, if given, specifies a time to analyze instead of the current time. The argument should be a cons cell containing two integers, or a list whose first two elements are integers. Thus, you can use times obtained from current-time and from file-attributes.
• sit-for, sleep-for now let you specify the time period in milliseconds as well as in seconds. The first argument gives the number of seconds, as before, and the optional second argument gives additional milliseconds. The time periods specified by these two arguments are added together. Not all systems support this; you get an error if you specify nonzero milliseconds and it isn't supported. sit-for also accepts an optional third argument nodisp. If this is non-nil, sit-for does not redisplay. It still waits for the specified time or until input is available.
• accept-process-output now accepts a timeout specified by optional second and third arguments. The second argument specifies the number of seconds, while the third specifies the number of milliseconds. The time periods specified by these two arguments are added together. Not all systems support this; you get an error if you specify nonzero milliseconds and it isn't supported. The function returns nil if the timeout expired before output arrived, or non-nil if it did get some output.
• You can set up a timer to call a function at a specified future time. To do so, call run-at-time, like this:

  (run-at-time time repeat function args...)
  

  Here, time is a string saying when to call the function. The argument function is the function to call later, and args are the arguments to give it when it is called. The argument repeat specifies how often to repeat the call. If repeat is nil, there are no repetitions; function is called just once, at time. If repeat is an integer, it specifies a repetition period measured in seconds. Absolute times may be specified in a wide variety of formats; The form `hour:min:sec timezone month/day/year', where all fields are numbers, works; the format that current-time-string returns is also allowed. To specify a relative time, use numbers followed by units. For example:

  `1 min'

  denotes 1 minute from now.

  `1 min 5 sec'

  denotes 65 seconds from now.

  `1 min 2 sec 3 hour 4 day 5 week 6 fortnight 7 month 8 year'

  denotes exactly 103 months, 123 days, and 10862 seconds from now.

  If time is an integer, that specifies a relative time measured in seconds.

To cancel the requested future action, pass the value that run-at-time returned to the function cancel-timer.