I was always wondering what defined the first day in the year in the Gregorian calendar. Then when hearing about this Sirius correlation looked up details about the previous calendar, Julian, and that also started the year with January 1, not with March as sometimes is said and assumed due to names like September and October (7, 8). So the chance is high that the Julian calendar was already fixed on Sirius. That would make sense as the Egyptian calendar begins the year also related to Sirius, there the heliacal rising, and as the Romans with their Julian calendar followed in time from the Egyptians and merged in the Hathor Temple of Dendera even visually due to the Roman Emperors depicted there as Pharaos, it really makes sense.