When should I replace the batteries in my Honeywell thermostat?

Install fresh AA alkaline batteries immediately when the 'REPLACE BATTERY' warning begins flashing on the display. The warning typically flashes about two months before the batteries are depleted. Even if the warning does not appear, you should replace batteries once a year or before leaving home for more than a month. If batteries are inserted within two minutes, the time and day will not need to be reset.