Format for time of day.

[hour12] is an optional placeholder for the hour on 12 hour clock (1-12)

[hour] is an optional placeholder for the hour on 24 hour clock (0-23)

{minute} is a required placeholder for the 2-digit minute (00-59)

[ampm] is an optional placeholder indicating AM or PM

Examples: "[hour12]:{minute} [ampm]" would correspond to a format like "12:33 AM" or "7:44 PM"

"[hour]:{minute}" would correspond to a format like "0:33" or "19:44"