take current date and

set its seconds to zero
set milliseconds to zero
increase minutes by one

for some number of tires to not loop forever
	if month matches the month pattern
		while that month doesn't change
			if weekday matches the weekday pattern or day of month matches the day of month pattern
				while day of month doesn't change
					if hour of day maches the hour of day pattern
						while hour of day doesn't change
							if minutes matches the minutes pattern
								yield cron hour
							else
								increase minutes by one
					else
						set minutes to zero
						increase hour of day by one
			else
				set hour of day to zero
				set minutes to zero
				increase day of month by one
	else
		set day of month to one
		set hour of day to zero
		set minutes to zero
		increase month by one
		increase counter of tries by one