New motherboard now clock falls behind

First of all, no one [other than you] has any idea what hardware you are running. Post your system specs.
Next the most likely cause would be a bad cmos battery. Generally these are a 2032 battery available anywhere ie walmart, computer store, office store, etc however since we do not know the mfg of the mb, it may be some other battery.

Sorry about the incompleteness of my question. I went into the BIOS and set the clock to the correct time and since then it has been holding the correct time in spite of being switched on and off several times so perhaps this has solved the problem.
Thanks for your help.