Africa/Cairo 2023-4-27 add 1 day, unix value is not correct.

[sirzdy]

Africa/Cairo 2023-4-27 add 1 day, unix value is not correct.

[gilmoreorless]

Yep, looks like a bug to me, I suspect it's the same as #409.

What's happening is that DST started for Cairo at 00:00 on April 28, jumping straight to 01:00. When Moment Timezone is provided that timestamp directly, it correctly calculates the new time:

moment.tz('2023-04-28', 'Africa/Cairo').format();
// '2023-04-28T01:00:00+03:00'

But when it's given the day before and adds a day, it incorrectly uses the old hour with the new offset, which is a time that technically doesn't exist:

moment.tz('2023-04-27', 'Africa/Cairo').format();
// '2023-04-27T00:00:00+02:00'
moment.tz('2023-04-27', 'Africa/Cairo').add(1, 'day').format();
// '2023-04-28T00:00:00+03:00'   WRONG, should be 01:00:00

I'm going to close this as a duplicate of #409, and you can watch that issue for an update of when the bug is fixed.

[sirzdy]

Thanks a lot!