Durations are written as a number followed by a unit, with no space between them.
Units
m is minutes, not months. Months use mo, so 6m is six minutes while 6mo is six months.
Combining units
Chain values together to build a more specific duration. Order them from largest unit to smallest.
Never mix in spaces or commas. 1d 12h and 1d,12h will both fail to parse.
Limits
Each command sets its own minimum and maximum. If a duration falls outside the allowed range, the command will tell you the limits instead of running. 