Bob, it's true that ISO-8601 set the standard as Monday as first day, but that's not culturally neutral. As you will see in the Wikipedia article on Week:
| System | First day of week | First week of year contains | Can also be last week of previous year | Used by/in |
|---|
| ISO-8601 | Monday | 4 January | 1st Thursday | 4–7 days of year | no | EU and most of other European countries |
| (Islamic) | Saturday | 1 January | 1st Friday | 1–7 days of year | yes | Much of the Middle East |
| (North American) | Sunday | 1 January | 1st Saturday | 1–7 days of year | yes | Canada, USA, China, Japan, Israel, most of Latin America
|
Some languages reflect a Sunday-first order: "
the Portuguese word for Monday is segunda-feira and the Greek [liturgical] word is Δευτέρα "devtéra" (second in order). Likewise the Hebrew name for Monday is yom-sheni (יום שני)."
So why is Monday first in Europe? This basically reflects the influence of Xtianity, aiming to align Sunday ("The Lord's Day") as the seventh day of the week so that the Ten Commandments would seem to refer to Sunday as the Sabbath, not Saturday as it was understood to be for centuries (although again, even languages like Spanish and Portuguese reveal the original, because they call Saturday sábado)
So, to reiterate, billions of non-Xtian people refer to other-than-Monday as the first day of the week. It's only the decidedly non-culturally-neutral Europe that does. It's hardly universal.
Bob writes:
Any particular religion should not enter into the consideration at all.
Exactly. But it does, by its very nature.
Numbering days is inherently fraught with religious overtones. Coloring them is not. And it's not just theoretic. When you call Sunday zeldei, it does indeed cause a visceral reaction in me ( My "a'unaisaire'e" in my previous letter was not merely hyperbole)