Below is a post that I copied & pasted from a buyer of the DT620CL... The directions from Intermatic suck & from the reviews left in here, the programming interface could have very well caused a few suicides... This is not a particularly difficult unit to program, but the thing that got me was the event on/off cycle as you will read below... And THANKS Chuck Pearson...
There are several secrets to programming this device. From reading the reviews you can tell that some people figured them out right away after reading the directions, some had difficulty, and some never figured them out and returned the device as defective.
Secret 1: OK doesn't mean OK. It means cancel the setting I just finished programing. To keep the setting you have to push PROG after setting the minutes.
Secret 2: An event is not an on-off cycle. It is just one time setting. To get an on-off you need to program two events. If you program an on time for event 1 and then an off time for event 1 you will find that the on time is gone. You can do on settings and off settings in any order. The device just executes the change of state when that time is reached for that day.
Secret 3: You have to push the ON/OFF button when you plug it in the first time after programming it. After that it operates by itself.
Secret 4: Dusk and dawn settings override time settings. I didn't set any dusk or dawn events so I didn't figure out the details of this one but if your device isn't going on and off when you expected it to, check your dusk and dawn settings.
Other than that I have one other small but easily remedied complaint for this particular unit... At the bottom of the unit where you have 2 110 grounded appliance grounded plug-ins, there is a 1/4"-3/8" X 1/8" thick lip that extends past the base of the unit. This lip will not allow any appliance access, with an oversized plug, like say a window unit air conditioner. Any appliance that has a normal size plug like the one pictured on this item will plug in perfectly fine. I am a civilian contractor in Afghanistan & I bought this timer to run a small air conditioner in my B-hut, that has an oversized plug that houses an internal re-setable overload breaker. I bought this timer because I am limited on power plug-ins, only 2 plug-ins per hootch. At any rate, the DT620CL takes up 2 plug-ins unless you tilt the unit. But back to the lip interference. The case of this unit is of coarse plastic. Unfortunately I'm not back at home, so I don't have access to my nice shop full of tools to trim the lip down. I used a Gerber multitool to nip the plastic lip down to the base of the unit. Very crude, but it worked & it did not crack or harm the case of the unit... A regular pair of pliers would have worked just as well I would imagine. Your best bet would be to take a dremel & small cutting wheel to trim the lip down.
This unit has 5 stars written all over it if they would fire the bozo who wrote the directions, but first make him pay for the divorces he's caused... Then fill in the injection mold at the factory where this stupid lip is molded. This lip adds no structural advantage to the unit, just makes it a PIA for us poor saps stranded in this lousy country...
Hope this review helps!
Chopper