Clone creates unequal object when DST starts on midnight

[yefrem]

TL;DR clone works incorrectly for an object pointing at the midnight DST start

There are several timezones that have DST start/end on midnight, e.g. Havana turns the clock 1 hour forward on Mar 8 00:00, which makes this time technically non-existent. When moving to this date with add(), moment is smart enough to understand it should be Mar 8 start. But if you clone the object, this info is lost and resulting object is not equal to it's source.

m = moment.tz('2020-03-01', 'America/Havana')
m.add(1, 'week')
console.log(m.format('YYYY-MM-DD')) // 2020-03-08
console.log(m.clone().format('YYYY-MM-DD')) // 2020-03-07