If you have to time something (and you don't want an external RTC or other timer) then you must choose a sleep mode which doesn't turn off the timers. That's the solution for the 'lowest power mode which has this capability'.
If you have to time something (and you don't want an external RTC or other timer) then you must choose a sleep mode which doesn't turn off the timers. That's the solution for the 'lowest power mode which has this capability'.