Power failure and digital clocks
I can think of two possibilities. 


Since you're apparently in a 60Hz region, if the clock counts power-line
cycles it would need to know if the mains frequency was 50Hz or 60Hz. 
If it thinks it is 50Hz but it actually is 60Hz then it would run fast by
exactly 20%. You don't say how long it's been running (I don't know your
time zone)but that would imply about 15 hours running, which is possible. If that setting has been corrupted by an ugly power cycle (and cheap supervisory circuitry and dubious programming) then it could default to 50Hz, which is the most common setting worldwide.  
If it has a power backup RC clock (low accuracy) that is intended to keep the clock reasonably close to being on for a short failure under battery or super-capacitor backup power, and the
surge zapped the mains clock circuit (quite plausible) then it would
run on the RC clock continuously, which could be 5% or 10% or 20% fast or slow (or anywhere inbetween). So if the power blipped off for 10 minutes the clock would be correct within a minute or two. 


In the latter case, the clock functionality is probably toast. In the former case, you might be able to find a secret setup EEPROM variable triggered by something like holding keys down as the unit is powered up or something like that. Good luck without instructions, but maybe there is info available somewhere. 

For anyone actually doing this kind of design, this answer points out a couple of things not to do. 


Don't depend on dubious circuitry to protect against mains surges
Don't use simple RC reset circuits when EEPROM corruption can cause problems. Enough units in the field and you will regret it.