Expression: When and when?

Calculation period: unified timing method adopts head-to-tail calculation.

Means: hours and minutes.

Different representations represent different results.

For example, the time after 9: 00 am15 minutes (calculation time): 9: 00 am15 minutes (9: 15).

How long does it take from 9:00 am to 10:30 am (time period): 1 hour 30 minutes.

Hope to adopt. Thank you.