It's true that a lot of theology that we might think is "ancient" or "traditional" isn't really. However, the Jewish year (currently 5777) is widely at least referred to across Jewish denominations.

This reckoning is called לבריאת העולם‎ or Anno Mundi in European cultures and does officially refer to the creation (בריאת). Wikipedia says that the current consensus about this timescale was fixed by Maimonides in 1178 CE.

https://en.wikipedia.org/wiki/Anno_Mundi

I should add that writing dates in the Jewish calendar doesn't necessarily imply that one using the calendar personally believes that it literally refers to the age of the world, but most users would probably agree that "Jewish tradition" in some sense has regarded it that way.

https://en.wikipedia.org/wiki/Dating_creation#Early_Jewish_e...

According to wikipedia the Christian calculation traditions started with the earliest Christians and continued through medieval European times https://en.wikipedia.org/wiki/Young_Earth_creationism#Biblic...

All orthodox Jews ascribe to this.

I'm not sure how you can claim this is a 20th-century interpretation as I'm currently looking at writings from ~2000 years ago (the Mishnah and Talmud) that discuss it.

I don't agree that all orthodox jews subscribe to it, although I do agree that it's a commonly held belief.

The universal values held by Orthodox Jews are the articles of faith of Maimonides ("Rambam")[1], which are included in regular prayers. Maimonides is, as a result, extremely well regarded among Orthodox Jews as a source of values.

Maimonides took the position that Genesis (Bereishis) was to be considered allegorical when its plain reading conflicted with science[2]. This was a source of debate among his contemporaries, and it's uncontroversially the case that he strongly believed this.

As a former Orthodox Jew, I don't think that Orthodox Jews are doing themselves any favors by teaching their children that if they believe that the Torah is not in conflict with science, they are violating basic, universal Orthodox values when Maimonides disagrees with that point of view.

[1]: https://en.wikipedia.org/wiki/Maimonides#The_13_principles_o...

[2]: https://en.wikipedia.org/wiki/Allegorical_interpretations_of...

Yeah, but orthodox Jews are like 10% of Jews.

As a conservative Jew, I think this view is a minority position amongst all the liberal movements.

True.

I was mostly stating that in regards to the viewpoint of orthodox Jews as espoused in the GP.

My main point was that it is not an idea that came about in the 20th century.