I have a globe 7 day programmable thermostat which I have had for approx 4 years. Now the time display keeps flashing as if there has been a power failure. I reset it and again a few hours later it is flashing again.

Have you checked to see if there are any batteries in your thermostat? Don't know what unit you have but many require batteries (often a couple AAs) that would need replacing after four years. Hope this works!