Thank you for wording it way better than I can
I think it is DST related since it started happening after ending DST.
Like you say, the interpreter of the web page somehow because of either a 23 or 25 hour cycle is off by one day and that leads even to the off-by-one-month with solar usage.
Btw: This is the regular website
See also this thread:
Ha!
Thanks for reminding me I have a possibility to look at the beta web page as well!
To my surprise the BETA page shows everything NORMAL!!
Today == TODAY!!!
And the new billing period:
As it should be!
So Sense has a beta channel.
But they choose to put the new changes directly in production.
And now the beta website is βnormalβ
and the stable/normal website is broken.