Duration doesn't work as expected

[AjaySewradj]

I'm trying to use the Duration object to create a countdown clock by using the minus function to subtract a second. But it seems that the minus function operates on the units (e.g. seconds) independently.

Steps to reproduce

var duration = Duration.fromObject({minutes: 1, seconds: 0})
var time = `${duration.minutes} : ${duration.seconds.toString().padStart(2, '0')}`

var newDuration = duration.minus({seconds: 1});
var newTime = `${duration.minutes} : ${duration.seconds.toString().padStart(2, '0')}`

Expected:
time: 1:00
newTime: 0:59

Actual:
time: 1:00
newTime: 1:-1

[icambron]

Yes, each unit is independent. Switch your third line to this in order to "reshuffle" the units:

var newDuration = duration.minus({seconds: 1}).normalize();

[RemyMachado]

@icambron
It seems the behavior is inconsistent. If I had to guess I would say that if the upper unit is present, then it's automatically subtracting from it, if not, then it goes into negative.
Please, check this codesandbox.