Sirius was not only important in ancient Egypt, where its heliacal rise in summer defined the new year, also today it plays an unofficial pivotal role for the calendar with its yearly midnight culmination happening at the new year's beginning since about 1901.

That's true regarding solar time at any location in the northern hemisphere. Solar time and local time differ by a few seconds to up to 3 hours in some locations, depending on the timezone definition.

The discussion I like to start here: Was this the anchor point for the Gregorian's Calendar?

Here a visualization of new year 2022 as seen from Giza:
[areo.info]

And as comparison the same at new year 1583 when the Gregorian Calendar begins:
[commons.wikimedia.org] (3rd image)

If you assume a constant proper motion of Sirius and a constant Earth axial precession, the timing is off by 17 minutes back then.



Edited 2 time(s). Last edit at 01/08/2022 05:17PM by Holger Isenberg.