Not really a bug but a feature!
When the clocks go forward like they did this morning 30th March in the UK, the day only has 23 hours.
When you scroll back to look at previous days in the Energy section, they also only have 23 hours.
So each “day” starts an hour later in the morning as you scroll backwards and only shows 23 hours.
It will no doubt correct tomorrow.
An unfortunate side-effect of the international infatuation with “daylight savings time”. I honestly wish they would stop doing it because modern technology has made the original need for it obsolete.
A potential “fix” would be to show 24 hours from 1am when clocks go forward and 24 hours from 23:00 the previous day when clocks go back? A bit of a hack though?!
Same “issue” here in Italy.
Another side effect, it also seems that all the previous “individual devices” usages stats, was shifed by one day. 
