Thermostat schedule does not follow programmed times; heating turns on/off at wrong times.

Safety first: No electrical work is required.

Steps to check:

• Set correct time and date: In the thermostat settings, ensure the current time, day, and (if applicable) year are correct. Enable automatic DST adjustment if supported.
• Review schedule: Go through each programmed period for each day. Ensure times are in the correct order and do not overlap. Correct any obvious errors.
• Check mode: Confirm the thermostat is in 'Auto' or 'Program' mode, not in 'Manual' or 'Holiday' override.
• Factory reset: If the schedule is corrupted, perform a factory reset and re-enter the schedule from scratch.

Resolution: After correcting time and schedule, monitor operation for 24 hours. If the thermostat still misbehaves, internal memory may be faulty and the unit should be replaced.