Incorrect datetime UTCLeapSeconds conversion

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?

Answer 1

[Cris LaPierre]

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]

I submitted a bug report.

[James Tursa]

TMW has replied that this bug will be fixed in the R2023b.