Fix pipe to calculate difference between time-out and time-in

[enriquezrene]

SubstractDatePipe is being used to calculate the number of hours/minutes representing the difference between time-out and time-in. This pipe has a bug since it is not considering the dates, only the times.

For example:

start-date: 13/05/2020T10:00:000Z
end-date: 14/05/2020T12:00:000Z

The result is going to be 2 hours which is wrong since the right value should be 26 hours.

[enriquezrene]

Not high priority since time-entries are allowed to start and finish in the same day for now.