A bit late posting but others might pick this point up. I am with Bulb and they say:- + During the winter, when the UK is on Greenwich Mean Time (last Sunday of October to the last Sunday of March), your off-peak electricity hours will be 00:30-07:30. + During the summer, when the UK is on British Summer Time (last Sunday of March to last Sunday of October), your off-peak electricity hours will be 01:30-08:30. THE FACTS When I last cycled through on the readings using the button on my electricity meter the time is displaying 21.08 which I assume is 22.08 BST However, the time stamp on my phone is 22.29. (I video all my readings each month). My phone/camera is set near to the exact 'real time' BST. THE QUESTION / POINT I RAISE So as the time displayed on my electricity meter is slow by 21 mins this means my off-peak electricity hours 'real time' BST will be 01:51 - 08:51 and GMT will be 00:51 - 07:51.