Question 1

What is the 24-hour format for common times?

Accepted Answer

Midnight = 0, 1 AM = 1, 6 AM = 6, noon = 12, 1 PM = 13, 3 PM = 15, 6 PM = 18, 9 PM = 21, 11 PM = 23. To convert any PM time: add 12 to the 12-hour value (except noon). So 7 PM = 7 + 12 = 19.

Question 2

Does this cross midnight correctly?

Accepted Answer

Yes. If subtracting the duration takes you past midnight (e.g. 12:30 AM minus 2 hours = 10:30 PM), the calculator correctly shows the previous day's time and labels the result as 'Previous day' so there is no ambiguity.

Question 3

What are practical uses for this calculator?

Accepted Answer

Recalling when you last took medication (took a dose at 3 PM, need to know when 6 hours prior was), timestamping a past event from a known current time, determining a meeting start time from its end time, or figuring out what time a shift started.

Question 4

How is this different from the 'Time in X Minutes' calculator?

Accepted Answer

The 'Time in X Minutes' calculator adds time forward to find a future time. This calculator always subtracts backward to find a past time. Both use the same underlying arithmetic — just in opposite directions.