[Possible cause] 1. AM or PM set incorrectly in program 2. AM or PM set incorrectly on the clock. 3. Voltage spike or static discharge. [Corrective Action] Check current clock and program settings including the AM or PM designations for each time period. If a voltage spike or static discharge occurs reset your thermostat following the instructions in your manual. [Symptoms] 
Thermostat does not follow program