Most modern heating systems are controlled by a timer or programmer. They have two channels, one for hot water and one for heating. Each channel can be set independently from one another in any combination of:
OFF - ON once per day - ON twice per day - ON constantly
Many have the ability to have different ON/OFF times for weekdays and weekends.
A few systems have the timer/programmer built into the boiler enclosure as a user control. For nearly all types you have to open a flap to access the setting panel.
Find your programmer and adjust it. If you don't have one it will be a very unusual installation.
Peccavi, December 2008
