[obspy-users] UTCDateTime and leap seconds?

Lion Krischer krischer at geophysik.uni-muenchen.de
Fri Mar 17 15:52:45 CET 2017


Hi Christian,


currently UTCDateTime is not aware of leap seconds. We have some
discussions online and the current plan is to enable it for time
difference calculations, e.g

time_a - time_b

If there is a leap-second in-between it will be reflected in that. Same
when adding a time and a duration.


Your example contains a leap second time which we will likely not handle
because neither our underlying time representation nor Python can
actually deal with these "60-second" times (there were some internal
discussions on the python dev mailing list but if I remember correctly
they deemed the problem not serious enough to deal with it). We'd
probably just raise an error in these cases.

It might be possible to add a flag "is_leapsecond" to the UTCDateTime
object and than gracefully handle these cases but this will likely bring
along quite some additional complexity.


It is indeed a bit problematic but it only matters for time difference
that have one or more leap seconds in between so the actual damage is
likely limited. But we should somehow find a proper way to deal with it.


Please join the discussion on Github if you have some more ideas:
https://github.com/obspy/obspy/issues/1084


Cheers!

Lion



On 17/03/2017 15:26, Christian Weidle wrote:
> Hi,
>
> as I ran across an issue on leap seconds elsewhere, I wondered if/how
> they are dealt with in the UTCDateTime object.
>
> In [73]: t0 = UTCDateTime(2017,1,1)
>
> In [74]: t0 -1
> Out[74]: 2016-12-31T23:59:59.000000Z
>
> ... while in principle t0-1 should be 2016-12-31T23:59:60.000000Z due
> to the recent leapsecond.
> With 27 leapseconds since 1972 this might be a problem in some use cases.
>
> Has this been considered somewhere in the development?
>
> Cheers
> Christian
>
>
>
> _______________________________________________
> obspy-users mailing list
> obspy-users at lists.swapbytes.de
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