It’s actually really simple, but for some reason I just keep having to look up some of these… so… finally… note to self…

Calculations

=X+Y =X+N =Y-X Etc.

12:45 - 9:55 = 2:50

Time to decimal

=X*24

2:50 * 24 = 2.83

Decimal to time

=X/24

2,83 / 24 = 2:50

Days, hours, minutes

d h:mm

11 19:20

Total hours and minutes

[h]:mm

283:20

Total minutes

[m]

17000

Regarding the formatting, without the brackets, it formats as regular time (total hours % 24). So, for example, 2 hours and 50 minutes multiplied by 100; with a regular time format (h:mm) it displays as 19:20; using brackets ([h]:mm) you get the correct 283:20, which is 11 days 19 hours and 20 minutes (hence the 19:20 from h:mm).