I learned about the ISO-8601 duration format today. It’s a way to represent a duration of time in a standard format.

For example, P3Y6M4DT12H30M5S represents a duration of 3 years, 6 months, 4 days, 12 hours, 30 minutes, and 5 seconds.

https://www.digi.com/resources/documentation/digidocs/90001488-13/reference/r_iso_8601_duration_format.htm