I don't have a timer and has two micro grows fully ready to be flowered. There about half a foot in height and have 4 27k CFL's on them, a fan for circulation and I used a large box and surrounded it with aluminum foil. I am is also Nuting the plants once a week with the recommended dose. Plants are healthy. The question is... My schedule conflicts with a perfect 12/12 rotation. Therefore I made a firm schedule of 10:30-10:30 on/off Mon-Thurs and 12:30-12:30 Fri-Sun This means...2 days of the week they will either feel a 10/14 or 14/10...Will this be a problem?
Do not try to control your lights manually, buy a timer. They are cheap and well worth it. Besides the timing issue you described (which wouldn't be 12/12 now, would it?), there also is the very real possibility that you will forget to turn the lights on or off, or you will be delayed or something (plenty of newbies on here all the time asking what to do because this happened). The answer is: buy a timer.
apples and oranges. I have a digital timer and analog timers. I prefer the analog timers for ease of use.
I find it is much harder to fuse an analogue timer. The amount of digi's I've owned in the past that just pop, even when run WELL under the recommended 13a load.