Re: taking Jan 1 as the beginning of the year was historically naive.
It's a fairly complicated set of events. "Years" can start at different dates. Academic years (at least in the UK), for instance, start with the Autumn or Michaelmas (YMMV) term. The church's year started on the assumed date of Christ's conception, 9 months back from Christmas, i.e. March 25, Lady Day. That also became the starting date for a lot of commercial arrangements. However there was also a tradition that January 1st was the start of the year so you may well find dates in the first few weeks of the year being given along the lines of 1722/3. I know of one published early C18th diary which starts years in January and some years are labelled in that fashion and some in modern fashion.
England and colonies stuck to the Julian calendar long after many countries had gone over to the Gregorian (but not all at the same time) and by 1752 the two calendars were 11 days out of sync. This was solved by omitting 11 days from September so the calendar for the start of that month reads 1 2 14 15 16 and January 1st was set as the start of the year in accordance with the Gregorian calendar.
This introduced a potential problem with contracts. That was solved by having the contracts which covered that period run for the appropriate number of days. So a contract taken out on March 25 in 1752 would expire on April 4th 1753 and a new contract would start on April 5th. The "loss" of 11 days was problematic in itself so it's not surprising that nobody wanted to tinker with changing contract terms as part of the legislation. On the basis of not fixing what wasn't broken, nobody has tinkered with it since so the UK financial year still runs from April 5th - and try to visualise the complications and expense it would cause to change that now.
Of course businesses are free to arrange their accounting years whenever they like and if a business thinks it's a good idea to go through the accounting year turnover when everyone's feeling a little under the weather, good luck to them.