Quiz time left (compare fixed time to now() time)

[surveyhub]

Hello Dears,

we had setup a quiz and it has a start and end time.
we need to show the time left to the quiz end.
we added the following xml

but it always return NaN
Kindly what is the issue

[Kal_Lam]

@surveyhub, maybe you wish to share your XLSForm with the community for some help?