Time­Cowan

Time

(current-posix-second)

Returns an 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:

• Is as accurate as reasonably achievable.
• Provides at least 1-second precision.
• Provides a range of at least 2³¹ seconds before and after the epoch.

Implementations SHOULD return an inexact value, allowing programs to deal in flexible precisions.

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.

Date and Time Arithmetic (WG2)

See TimeAdvancedCowan.

Time Durations and Periods (WG2)

See TimePeriodsCowan.

Time formatting (WG2)

See TimeFormattingCowan.