Found this on http://www.partsarena.com/baxi/System/index.htm
Users operating instructions for the Olympic replacement programmer
Leave these instructions with the User
To gain access to the clock pull off the clear plastic cover.
The outer ring of the clock is marked as a 24 hour clock.
The time set position is in the top right hand corner of the clock, carefully move the pointer on the clock clockwise until the correct time of day is indicated on the 12 hour clock (if a.m. a number between 1 and 12 will be at the top right hand corner, if p.m. 12 and 24 will be at the top right hand corner).
The small 'tappets' around the edge of the clock are used to set the periods when you require the boiler to operate. These are easily moved by lifting them off away from the outer clear plastic ring around the clock.
Only use four tappets (two red and two blue), keep the remainder supplied as spares.
With the Timing Selector switch in the central position (Twice a day) and the Service Selector switch in either the Hot water or Heating and Hot water position the boiler will operate between two tappets of different colours and be off between two tappets of the same colour.
Always use the two blue tappets for the night time off period and the two red tappets for the day time off period.
A typical setting would be as follows:
Blue tappet at 7 (on)
Red tappet at 9 (off)
Red tappet at 16 (on)
Blue tappet at 23 (off)
This would allow for the boiler to operate between 7 a.m. and 9 a.m., switch it off between 9 a.m. and 4 p.m., allow it to operate between 4 p.m. and 11 p.m. and switch it off between 11 p.m. and 7 a.m., see Fig. 1 overleaf.
richard harpole, October 2008