negative values when calculating number of days

[Magnus]

I have two different days in the system. PromisedDeliveryDate and DeliveredDay. I want to calculate how many days that differ between them.

This is the expression I'm usingand it works for the most part. The problem is when I subtract 1 February with 31 January for example. This should give me a result of 1 since it differs 1 day. instead it gives me a result of -30. Does anyone know why?

=interval((day(DeliveredDate)) - (day(PromisedDeliveryDate)), 'D')

[tresesco · Accepted solution]

That is because you are asking to subtract 31 from 1. To get your desired result, you just need:
=interval(DeliveredDate - PromisedDeliveryDate, 'D')

'D' format code would take care of the rest.

[Magnus]

ty