Why is Sankranti on the 15th this year instead of the 14th?

The story

Why is Sankranti on the 15th this year instead of the 14th? I visited Gavigangadreshwara Temple today, and they said “Sankranti is tomorrow.” That sent me down a rabbit hole that revealed something fascinating about how we measure time. There are two types of calendars: tropical (based on seasons and equinoxes) and sidereal (based on the positions of stars). Uttarayana follows the tropical calendar; it’s the winter solstice, always around December 21st. But Makar Sankranti follows the sidereal calendar, marking when the sun enters Capricorn relative to the stars. Here’s where it gets interesting: Earth wobbles on its axis like a spinning top, this is called axial precession. This creates a 20-minute difference between the tropical year and sidereal year. Over 70 years, those 20 minutes add up to one full day. About 1,700 years ago, Uttarayana and Sankranti happened on the same day. But because of Earth’s precession, Sankranti has been slowly creeping forward in the calendar. The stars haven’t moved. Sankranti hasn’t moved. Earth is just wobbling. I made a plot showing this drift over the centuries ; you can see exactly how this one-day shift happens. ಮಕರ ಸಂಕ್ರಾಂತಿಯ ಶುಭಾಶಯಗಳು! 🪁 ಈ ವರ್ಷ ಸಂಕ್ರಾಂತಿ ೧೫ಕ್ಕೆ ಯಾಕೆ? ೧೪ಕ್ಕೆ ಅಲ್ಲವೇಕೆ? ಗವಿಗಂಗಾಧರೇಶ್ವರ ದೇವಾಲಯಕ್ಕೆ ಹೋದಾಗ ಅವರು “ಸಂಕ್ರಾಂತಿ ನಾಳೆ” ಅಂದರು. ಆಗ ತಿಳಿಯಿತು; ಉತ್ತರಾಯಣ ಮತ್ತು ಮಕರ ಸಂಕ್ರಾಂತಿ ಬೇರೆ ಬೇರೆ ಪಂಚಾಂಗಗಳನ್ನು ಅನುಸರಿಸುತ್ತವೆ. ಭೂಮಿಯ ತಿರುಗುವಿಕೆಯಿಂದಾಗಿ, 70 ವರ್ಷಗಳಿಗೊಮ್ಮೆ ಒಂದು ದಿನದ ವ್ಯತ್ಯಾಸ ಬರುತ್ತದೆ. ನಕ್ಷತ್ರಗಳು ಚಲಿಸಿಲ್ಲ. ಸಂಕ್ರಾಂತಿ ಚಲಿಸಿಲ್ಲ. ಭೂಮಿ ಸ್ವಲ್ಪ ತೂಗಾಡುತ್ತಿದೆ ಅಷ್ಟೇ! 🌍 ಮಕರ ಸಂಕ್ರಾಂತಿಯ ಹಾರ್ದಿಕ ಶುಭಾಶಯಗಳು! 🪁​​​​​​​​​​​​​​​​