It depends what kind of business... there are all sorts of weird and wonderful accounting / financial calendar inventions like the 4-4-5 calendar, fiscal years ending in June, bond day count conventions like 30/360, etc.

I do take your point though. I've always found it quite surprising just how universal various arbitrary/western things are like, as you say, the western gregorian calendar, seconds/minutes/hours, SI units for measurement. In a world with so many unintelligible languages and disagreements, you'd think there would be more folks out there doing, I dunno, a 10 day week, or some non-hour/minute system, etc.