When I programme my video recorder using VideoPlus, it brings up programme start and finish times, transmission date and channel number. If you're looking for a slightly more technical explanation try
http://tallyho.bc.nu/~steve/videoplus.html
.
A refinement to the system is PDC (Programme Delivery Control) which works on the five main terrestrial channels but is not compatible with digital TV as yet. The idea of PDC is that it reacts to signals given out as a programme starts and ends thereby ensuring that even if your chosen transmission is delayed, it'll still record.