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.
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.
For Giza the match is really good for 2021 with only 56 seconds difference towards local time. For Greenwich it's a 3 minute difference these years, was better in 1900 with only a few seconds.
The mystery: How to explain this coincidence that the Sirius Midnight Culmination happens at the beginning of the Gregorian's Calendar's new year beginning? Or, maybe it is just random...
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To explain midnight culmination: Culmination of a star is the time when it is highest in the sky above the horizon during the night. At that time it crosses the local meridian, the vertical line above true South direction. That happens at different times every day for any star. Sometimes the culmination happens at midnight, like on new year's start for Sirius. ASP in the image is the antisolar point, added here to show that the local time matches the solar time. For other locations the ASP is more right or left of the meridian at midnight local time. Having a star near the ASP has some practical meaning for observations as it is usually the darkest location at that time.
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.
For Giza the match is really good for 2021 with only 56 seconds difference towards local time. For Greenwich it's a 3 minute difference these years, was better in 1900 with only a few seconds.
The mystery: How to explain this coincidence that the Sirius Midnight Culmination happens at the beginning of the Gregorian's Calendar's new year beginning? Or, maybe it is just random...
To explain midnight culmination: Culmination of a star is the time when it is highest in the sky above the horizon during the night. At that time it crosses the local meridian, the vertical line above true South direction. That happens at different times every day for any star. Sometimes the culmination happens at midnight, like on new year's start for Sirius. ASP in the image is the antisolar point, added here to show that the local time matches the solar time. For other locations the ASP is more right or left of the meridian at midnight local time. Having a star near the ASP has some practical meaning for observations as it is usually the darkest location at that time.