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encode-universal-time

encode-universal-time function

Syntax:

encode-universal-time second minute hour date month year

&optional time-zone

→ universal-time

Arguments and Values:

second, minute, hour, date, month, year, time-zone—the corresponding parts of a decoded time. (Note that some of the nine values in a full decoded time are redundant, and so are not used as inputs to this function.)

universal-time—a universal time.

Description:

encode-universal-time converts a time from Decoded Time format to a universal time. If time-zone is supplied, no adjustment for daylight savings time is performed.

Examples:

(encode-universal-time 0 0 0 1 1 1900 0) → 0 
(encode-universal-time 0 0 1 4 7 1976 5) → 2414296800 
;; The next example assumes Eastern Daylight Time. 
(encode-universal-time 0 0 1 4 7 1976) → 2414293200

See Also:

decode-universal-time, get-decoded-time

Expanded Reference: encode-universal-time​

Encoding time components into universal time​

encode-universal-time converts individual time components into a universal time integer.

;; Encode midnight January 1, 2000 UTC
(encode-universal-time 0 0 0 1 1 2000 0)
=> 3155673600

Round-trip with decode-universal-time​

Encoding and then decoding yields the original components.

(multiple-value-bind (sec min hour day month year)
    (decode-universal-time
      (encode-universal-time 30 45 14 25 12 2024 0) 0)
  (list year month day hour min sec))
=> (2024 12 25 14 45 30)

Using the local time zone​

When the time-zone argument is omitted, the local time zone is assumed.

;; Encode in local time
(integerp (encode-universal-time 0 0 12 1 6 2025))
=> T

Encoding the epoch​

Universal time 0 corresponds to midnight January 1, 1900 GMT.

(encode-universal-time 0 0 0 1 1 1900 0)
=> 0

Computing time differences​

Universal times are integers, so you can compute differences directly.

(let ((t1 (encode-universal-time 0 0 0 1 1 2025 0))
      (t2 (encode-universal-time 0 0 0 2 1 2025 0)))
  (/ (- t2 t1) 3600))
=> 24