read, study and understand blink without delay.
read about INT unsigned int and long and such
set a separate counter for each time,
15 , 30, 45, 60, 120 and 180 minutes and 1 second pulse
when an event happens, (switch?) each counter would come into play.
on long events, I have used a clock, the old electric style with hands. turn the power on at the start, i will run for those times, at the end of the cycle, the power fails and when you come back you have an indicator of the length of time of operation.
used to do that to test how long a battery would last.
just giving you some clues.