I'm guessing that if in your profile you don't check the box "Automatically check if my time zone is in DST", CW will think you're on permanent GMT? Basically you would want this if you're in Iceland. Not the shops! I'm not sure how CW's options would cope with users in Southern hemisphere countries where DST is used, but there are probably few of those on a site about canals in the UK.
In my work in IT I've had to learn quite a lot about time zones, and I can assure you it gets very messy in certain countries, notably Australia, Mexico, USA, Canada, Brazil, Argentina. But Argentina have tidied things up a bit in recent years. A special mention should go to Nepal, the only country I know of that uses an odd quarter hour. In Europe things are relatively simple; almost everyone puts clocks forward on the last Sunday in March, back on the last Sunday in October. The exceptions are Iceland on GMT, Russia which decided, in 2012 I think it was, to stay on permanent summertime so for example Moscow and much of European Russia is permanently GMT+4, and Kazakhstan which is GMT+6. I count Kazakhstan as in Europe because they are for football purposes, they're in UEFA.
Anyway, I digress. Computers, mobile phones and clocks based on radio signals should all pick up clock changes automatically.
You have to tell a computer or phone which time zone you want to be in, but a clock will be built to follow one signal, which in the UK means Althorn in Cumbria, it was moved from Rugby in 2007.
Footnote to the above; technically I should have talked about UTC not GMT. The difference between them is only a fraction of the second, and the reason only matters to scientists. For the purposes of time zones treat them as interchangeable.