On Sat 18 Mar 2017 23:41, Zefram <zef...@fysh.org> writes: > Computing the duration of the period between two UTC times, using > SRFI-19 mechanisms: > > scheme@(guile-user)> (use-modules (srfi srfi-19)) > scheme@(guile-user)> (define t0 (date->time-utc (make-date 0 59 59 23 30 6 > 2012 0))) > scheme@(guile-user)> (define t1 (date->time-utc (make-date 0 1 0 0 1 7 2012 > 0))) > scheme@(guile-user)> (time-difference t1 t0) > $1 = #<time type: time-duration nanosecond: 0 second: 2> > > The two times are 2012-06-30T23:59:59 and 2012-07-01T00:00:01, so at > first glance one would expect the duration to be 2 s as shown above, > the two seconds being 23:59:59 and 00:00:00. But in fact there was > a leap second 2012-06-30T23:59:60, so the duration of this period is > actually 3 s. The SRFI-19 library is aware of this leap second, and > will compute the duration correctly if it's translated into TAI: > > scheme@(guile-user)> (time-difference (time-utc->time-tai t1) > (time-utc->time-tai t0)) > $2 = #<time type: time-duration nanosecond: 0 second: 3> > > The original computation in UTC space should yield a result of 3 s, > not the 2 s that it did. Since 1972, the seconds of UTC are of exactly > the same duration as the seconds of TAI. (They're also phase-locked to > TAI seconds.) Thus the period of three TAI seconds is also a period of > three UTC seconds. It is not somehow squeezed into two UTC seconds.
Makes sense to me. Would you like to submit a patch and test case? I would be happy to apply it. Andy
