Yearly Distance Record Attempt (Tommy Godwin - 75,065mi/120,000k)

They're an addendum to these:
http://ultracycling.com/sections/records/docs/UMCA_records_packet_2015.pdf

which have a proposed start date field in the entry but there's no mention of whether or not it's a rolling 365 days other than their definition of a year comment. It sounds like it could roll on forever, in theory.

but does the start have to be offically declared?

That's the question.

If not, then the 365 days could be deemed to start before the rider actually started, so they just covered no miles in the first days.