Day and Night Mode can’t be set differently for each day of the week so most people will set their modes to All.
Most people want the heating to drop down at night and come up during the day, so they’d only set Night Mode. You’d only set Day Mode if you routinely wanted the heating to drop down during the day. If you have a full-time job, for example.
We have a more in-depth guide on our dedicated site for Moosewerks, Alde’s UK HQ.