I was a Basque in my previous lives…
A three-day week!!!… Whoaaa!… Unique on this planet for their language, the Basques are also the only culture in which the time was divided in units of successive groups of three days… That is, the Basque week, before their Christianisation and before their language started to be written, had only three days!…
This is obvious from the surviving ancient names of the days of the week in the Batua dialect:
Monday : Astelehena – first of the week (aste=week, lehen=first)
Tuesday : Asteartea -middle day of the week (artea=middle)
Wednesday: Asteazkena – last day of the week
Thursday : Osteguna or Orzeguna – day after the week is over (egun=day, oste=after).
As for the names for Friday, Saturday and Sunday, they have an unclear etymology, seem to have been added later, and some were clearly influenced by the Christian division of time.
Now I even think that I remember how in previous lives I used to say every third day: ”Thank God it‘s Wednesday!…“