Central Heating programmers

British Summer Time started here today so I went round putting all watches, clocks, oven timer, microwave etc to the new time. Eventually I made it to the central heating programmer and I found it had automatically adjusted to the new setting. When I looked up if it mentioned this in the booklet provided it said it was factory set to cater for time changes.

Well that’s great, but how do they do that? BST doesn’t start at the same date each year, surely they can’t set it up for all the different dates that BST/GMT start in the next x years.

I know my rather ancient video recorder will pick up a signal via the television and adjusts accordingly but my c/h programmer hasn’t got any facility to pick up a remote signal.

And what happens when we get a power cut, the programmer will have no power and even if it was keeping the date in its memory when powered all that will be lost. As far as I know there’s no battery back-up. I know I can manually alter the time but this is so convenient.

Am I missing something obvious (wouldn’t be the first time) and can anyone explain in relatively simple terms how this is achieved.

According to Wikipedia, BST starts the last Sunday in March every year. Once you know the date, calculating the day of the week is trivial. Then the logic is as simple as, “If it’s between March 26 and 31, and a Sunday, reset the clock.”

Incidentally, they just changed the start of Daylight Savings Time here in the US. Most things can be re-programmed pretty easily, but all sorts of embedded systems are still stuck on the old system. Amazingly, complete disaster has thus far been avoided. Important things tend to be set to GMT anyway.

Fair enough, that makes sense. I’ve re-read the booklet again and found that after installation you have to input the date as well as the time. This was obviously set by the guy who installed the programmer. It then follows that if the unit now loses power I’ll have to do the same. My excuse for for not realising the date was part of the details inputted is that it doesn’t appear on the normal display.

Thanks for your reply.