@Tyler-Brown Hey Tyler,
I think using the time in seconds would be very useful for you.

On the arduino that controls both your lights and your sprinklers seperately. You can shoot the time from your omega to the arduino constantly.
You then have an arduino sketch that is waiting for those specific numbers to come in:

#for sprinklers
If seconds is >= (6am in seconds) and <= (6:05 in seconds)
Turn Sprinkler on
#for Lights
else if seconds >= (dusk in seconds) or <= (dawn in seconds)
Turn Lights On