How can Thomas ensure his vegetables receive 18 hours of light and 6 hours of darkness?

Question

Thomas has two light bulbs for his home garden which have the option of 4, 6 and 12 hour two-way timers.

The two way timers allow for the light to be on for the selected amount of time and off for the same amount.

How can Thomas ensure his lights get 18 hours of light despite his lights only having 4, 6 and 12 hour options?

Answer 1

One 12 hour bulb starting, for example, at midnight and off at 6:00. On again at noon and oft at 6:00 pm.

One 6 hour bulb starting at 3:00 am and off at 9:00 am. On again at 3:00 pm and off at 9:00 pm.