What is the difference in H:mm:ss and HH:mm:ss in time formats?

I am trying to figure out the time format used on my computer if it is 12hour format or 24hour format and found this solution :

Dim strFormat As String = System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat.FullDateTimePattern 

The Result is yyyy'年'M'月'd'日' H:mm:ss

I am having confusion between this H:mm:ss and this HH:mm:ss

Is there any difference in the format of the time displayed?

1 Answer

Is there any difference in the format of the time displayed?

Yes.

• HH is 24-hours, with a leading zero for the hours 0-9.
• H is 24-hours without a leading zero for the hours 0-9.
  • Using H is not ISO 8601-compliant. ISO 8601 requires 2-digit date and time components with leading zeroes.

So if the current time is 0945h then H:mm will render 9:45.

So if the current time is 0945h then HH:mm will render 09:45.

So if the current time is 1945h then H:mm will render 19:45.

So if the current time is 1945h then HH:mm will render 19:45.

Other important notes:

• M and MM is months, not minutes.
• m and mm is minutes not months.
  • There are few (if any) reasons to ever use m, so always use mm!
• h is 12-hour clock hours without a leading zero.
  • Whenever you use h you must use tt to denote AM/PM, otherwise you'll have ambiguous output.
• hh is 12-hour clock hours with a leading zero.
  • Avoid using hh because (I believe) that today people expect two-digit times to be using a 24-hour clock.
  • As with h, you must also use tt to avoid AM/PM ambiguity.