After power outage, digital clock on St. George double wall oven model #deo5 needs resetting. I have no manual so no idea how to do

SOURCE: Cannot set clock Model RBS245PDB2

you need to replace the clock timer board..

SOURCE: Dim LCD's on DCS Double Wall Oven

Had the same problem last week - called DCS (which automatically transferred me to Fischer-Paykel) and was able to order the part from them.  They knew exactly what it was, and shipped to me in CA from CA, it was less than $90.  Just installed it, and the new one works swell.  One suggestion - I drew with a Sharpie on one side of each of the three parts that plug into the board to help align the new one, and to install the wide ribbon cable (not really a cable, but you'll know what I mean), pull up on the two side pieces and the ribbon pulls right out.  Keep it up and slide the new one in and then push the black piece down.  That was the only part that took me a minute to figure out.

SOURCE: instruction manual for Westinghouse wall oven

Obtained info from retailer

SOURCE: chef classic wall oven with digital clock change time?

Press the TIMER button (the leftmost one with a little bell icon) and the "cooking" button (the one next to it with a "hot saucepan" icon) briefly at the same time. Within four seconds start changing the time with the + or - buttons. When you have the correct time just leave it and it will leave time setting mode four seconds after the last button press.

SOURCE: turn off the timer on an old imperial st george

I have this exact same oven and this "feature" annoys me no end. To turn it off ... turn the clock dial to PAST the time that the timer dial shows. EG: If your timer dial is showing 6, turn the clock dial so that it rolls past 6 o'clock. This will pop out the timer dial and thus turn off the timer, allowing you to use the oven normally.

To stop accidentally pushing/turning that timer dial, I removed the knobs. Good luck.