A programmable thermostat will allow you to change the temperature set points depending on the day of the week and the time of day. Most people want a 5 + 2 programmable thermostat, which will allow for a weekday schedule and a weekend schedule. These are available at most hardware stores.

You should be setting the occupied temperatures to lower than 68 in the winter and higher than 78 in the summer. The more extreme, the better from a heating and cooling standpoint. For unoccupied setpoints, the heating should be below 65 and the cooling should be above 83.

You can set the thermostat to be unoccupied while you are at work, and then to turn on heating and cooling equipment shortly before you will be home. You can also set it to unoccupied when you will be away.