An odd question, but what is the time from radio 4? Looking at duel tariffs and when they change high to low rate?

I have read all I can find about radio 4 and tele switching, but can't find if this changes when our clocks change. It all started when I decided to get a smart meter fitted, and once fitted may as well get duel rate and recharge my 3.2 kWh batteries over night as well as using solar, this seems to work well I see a dip in state of charge between 8 am and 10 am, down to maybe 50%, but it means cheap electric most days last to between 9 pm and midnight. Clearly winter it will cut of earlier, but the cheap 8.95p rate 0 to 5 am seems to have made a huge difference, mainly as I can start using power from the moment I get up.

However my IHD (in home display) and the Phone app do not agree. The IHD shows BST, but the app shows I am using high power at end of each day, so seems to be showing UTC, I have changed charge time now to 1 am to 5 am to be on safe side, but I have tried ringing British Gas in the past, and been stuck on the phone for ages, and now changed it does not really matter.

However this could affect many others, with storage heaters or EV's. So wondered what time smart meters use?

Traditionally time switches were always on GMT as the heating was mainly used in the winter and it would have been an impossible job to change all the mechanical switches every time the clocks changed. When I used to work as an installation inspector for the local board you had to remember to always set them to GMT.
I dont think anything will have changed.

E7 times are normally 12 midnight till 7am, however teli switching/ integral time clocks in meter are staggered by approx 30mins so loads across the grid are not simultaneous. I always advise setting timers etc to the actual time on the meter not your own clock or watch.
Its sensible you chose the times you have to hit the O/P confidently

The problem is not GMT (UTC) or BST (DST) it is the not knowing what the times are, I was told to start with midnight to 8 am, then sorry no it's 5 am and now sorry it's 1 am to 6 am so for me easy set to charge 1 am to 5 am so when clocks change with my software, it is still within the cheap tariff time.

My state of charge is as shown, the dip rarely hits the 10% at least in summer, so it does not matter if I loose an hour. Most days solar will kick in before the dip hits 10% however I am charging a small 3.2 kWh battery, at 2 kW, those with EV chargers or storage radiators will have more of a problem as they are using more.