The timer controls are set for am and pm sections.
They start up OK for am but don't switch off until end of pm session.

Sandy, November 2016

I think the time controls are external to the boiler. Check these are set to operate twice per day: On1 to Off1 then On2 to Off2. It sounds like you have them set for once per day: On1 to Off2.

It should be easy enough to find a manual for your timeswitch / programmer

Anon, November 2016