Why are half-hourly time-slots showing more than once, or missing from my online account day view?

Time slots will be shown more than once when clocks go back one hour in autumn for Daylight Savings (DST). On this day, two additional time slots will be displayed, and you'll see a total of 50 time-slots instead of the usual 48.

Conversely, when the clocks go forward in spring, the corresponding time slots for that hour won't be shown. You'll see 46 time slots displayed on this day.