Understand the distinction
A total covering thirty-one days and one covering twenty-eight days do not describe identical durations. Season, occupancy and the tasks performed can also differ. Simply sorting the totals may obscure these basic differences before any household explanation is considered.
Put it in your home notes
Record the start and end dates beside each total. A per-day calculation can be a descriptive aid, but retain the original totals and note unusual conditions. Do not use that normalisation alone to declare that an appliance or building alteration caused a change.