This site is a static rendering of the Trac instance that was used by R7RS-WG1 for its work on R7RS-small (PDF), which was ratified in 2013. For more information, see Home. For a version of this page that may be more recent, see TimeCowan in WG2's repo for R7RS-large.

Time­Cowan

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2010-12-06 11:02:40
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Calendar Time

(current-posix-second)

Returns a rational number representing the current second of the Posix epoch, which began on 00:00:00 on 1 January 1970, Coordinated Universal Time but excludes all leap seconds. Implementations SHOULD return a value that:

If the implementation cannot provide the time when current-posix-seconds is called (either temporarily or permanently), it MUST return #f.

Assuming the number of leap seconds between 1972 and 2011 was typical (not necessarily a safe assumption), there is about a 1 in 10-8 probability that a computation of elapsed time made by calling this procedure twice will be off by 1.

Elapsed Time

(elapsed-time)

Returns an exact integer representing the number of jiffies (arbitrary elapsed time units) since an arbitrary epoch, an implementation such as the time the program started running, the operating system was booted, or anything else. Leap seconds are not excluded. Implementations SHOULD return a value that:

(jiffies-per-second)

Returns an exact integer representing the number of jiffies per SI second. This value is an implementation-specified constant.

Date and Time Arithmetic (WG2)

See TimeAdvancedCowan.

Time Durations and Periods (WG2)

See TimePeriodsCowan.

Time formatting (WG2)

See TimeFormattingCowan.