Most time of use electricity meters are fairly dumb things. To know when the clocks change they’d have to know the date as well as the time and thus when the last weekends in October and March are. And to know the correct time they’d have to sync with a radio signal or something. They’re generally far more basic than that and simply switch counters twice or six times a day, and the internal clock will lose or gain unless someone put it right occasionally. Mine is ten minutes fast at the moment but it’s losing and will be right time in about five years if nothing changes. Altering the timing on the heating twice a year isn’t such a huge task.