The beginning of Spring (Astronomical/meteorological) yesterday is tied in with the creation of the calendar system and why midwinter is on the December Solstice while midsummer is on the June Solstice in the Northern Hemisphere.

https://sol24.net/data/html/SOHO/C3/96H/VIDEO/

Aside from the daily change in the position of the stars and star trails centred around the star Polaris, there is an annual change in the position of the stars parallel to the orbital plane.

Everything to the left of the Sun is an evening appearance from the surface of a rotating Earth, while everything to the right is a morning appearance. The stars close to the orbital plane naturally transition from an evening to morning appearance as the Earth travels around the Sun, so this was observed in antiquity as a heliacal rising of a star or group of stars.

".. on account of the procession of the rising of Sirius by one day in the course of 4 years,.. therefore it shall be that the year of 360 days and the five days added to their end, so one day shall be from this day after every four years added to the five epagomenae before the new year" Canopus Decree 238 BC.

Whereas the Ptolemaic framework relies on the motion of the Sun through the 12 constellations, the Decans system relies on a new group of stars appearing every ten days at dawn, with 36 groups of stars making up the year with five days between the old and new year.

https://themathematicaltourist.wordpress.com/2012/10/13/the-decans-in-senenmuts-tomb/

Working with old and new observations takes a little time; however, with the extra day and rotation coming up on February 29th, contributors here have an opportunity to put a satisfying narrative together and explain how the 365/366-day calendar system emerged from external cyclical observations and the motions of the Earth behind those cycles.