I've programmed about 15 of the 436/536 units. During doing so I've had at least 2 of them give me issues when setting the day on the clock. It goes thru the first few steps and then gets to the day setting and it tells me Invalid Range please press any key to continue. I first thought maybe I was crazy but every single day or number I entered did not let me proceed past this step. I wound up hitting a combination of buttons, I think function and something else and it wound up bypassing the clock.
I was then able to go in and go to the settings menu and set the clock again and this time it worked without issue, it let me put the day of the month in with no problem.
I was then able to go in and go to the settings menu and set the clock again and this time it worked without issue, it let me put the day of the month in with no problem.