# Incorrect datetime UTCLeapSeconds conversion

7 views (last 30 days)
James Tursa on 7 Aug 2023
Commented: James Tursa on 9 Aug 2023
I am working with leap second data, and as part of the calculations I did this for a particular leap second:
dt1 = datetime(1972,6,30,23,59,60,'TimeZone','UTCLeapSeconds')
dt1 = datetime
1972-06-30T23:59:60.000Z
dt2 = datetime(dt1,'TimeZone','UTCLeapSeconds')
dt2 = datetime
1972-06-30T23:59:59.000Z
dt2.TimeZone
ans = 'UTCLeapSeconds'
dt1 - dt2
ans = duration
00:00:01
Well, you can see what happened. Even though the input and output time zones are both 'UTCLeapSeconds', the datetime( ) function has changed the time of this and jumped backwards 1 second. So to get around this I am forced to write code like this:
if( isequal(dt1.TimeZone,'UTCLeapSeconds') )
dt2 = dt1
else
dt2 = datetime(dt1,'TimeZone','UTCLeapSeconds')
end
dt2 = datetime
1972-06-30T23:59:60.000Z
dt1 - dt2
ans = duration
00:00:00
Looks like a bug to me, but does someone have another explanation for why this might be happening?

Cris LaPierre on 7 Aug 2023
Edited: Cris LaPierre on 7 Aug 2023
Potentially a bug, which you can report here: https://www.mathworks.com/support/contact_us.html
It looks like you have applied the time zone twice. You can do this instead:
dt1 = datetime(1972,6,30,23,59,60,'TimeZone','UTCLeapSeconds')
dt1 = datetime
1972-06-30T23:59:60.000Z
dt2 = dt1
dt2 = datetime
1972-06-30T23:59:60.000Z
dt2.TimeZone
ans = 'UTCLeapSeconds'
dt1 - dt2
ans = duration
00:00:00
James Tursa on 7 Aug 2023
I submitted a bug report.
James Tursa on 9 Aug 2023
TMW has replied that this bug will be fixed in the R2023b.