Why does the date start at 3/1/99 on XT models?
ChronTrol represents time internally in 24-hour format. Time runs from zero hours (midnight) to 23:59:59, then rolls back over to 00:00:00. (How the time is displayed is up to the user. In most cases, the time is displayed as 12-hour am-pm, just like a wall clock.) ChronTrol keeps the date internally in “ordinal date” format; the date runs from day 0 to day 364. Right off the bat, you can see that dates from March 1 onward have a different ordinal date in leap years. The ChronTrol XT model is required to do some pretty intensive calculations when it comes to cycles that extend past 24 hours. For instance, if you program a circuit to come on for two days out of every three, starting at 5 p.m. on February 28, will it go off at 5 p.m. on March 2? It helps to know if it’s a leap year, because the circuit will actually go off on March 1 if it is. The reverse is just as cumbersome – if you say explicitly “Turn on Feb. 28, turn off Mar. 1, and repeat every 3 days,” the circuits will do just t
