[owl57]

> An article written in Arabic, or Hebrew, or Tamil, or Malay may use the respective different calendars instead, as familiar to the readers.

Extrapolating from the only example I know, I wouldn't bet on it.

Before moving to Israel I knew that Rosh HaShanah (Hebrew New Year) is a public holiday and Gregorian New Year isn't, so I expected Hebrew calendar to be somewhat visible in everyday life or at least in official documents. Turns out, with the exception of holidays — to some surprise, including the decidedly secular Independence Day — it really isn't, everyone uses Gregorian.

[nine_k]

This is somehow expected when we talk about modern Israel. Maybe it would be less so when describing events of 1006 AD, if descried by contemporaneous Jewish sources.

Again, this a difference between astronomy and history points of view. In natural sciences, one would expect the now-universal units that originated in Western science: Julian calendar, SI units, times in UTC, etc. In historical and otherwise localized studies, I would expect a local / period-salient calendar, local units as reflected in the period's documents, etc. Converting these into exact modern dates and units is sometimes hard, and subject to a debate among historians.