I have a question about observing tithis like Ekadashi when living outside of India. Since tithis are based on the moon’s position and not fixed solar calendar days, how should I determine the correct date for fasting or spiritual observance in another country?

For example: If Ekadashi falls on Monday, July 21 in India, and I live in the U.S. Central Time Zone (CST), which is about 10.5 hours behind IST, should I follow:

The same calendar date (July 21) as India regardless of time zone? Or

The actual local tithi timing based on CST, which might mean that Ekadashi could begin the evening before (e.g., Sunday, July 20, 7:30 PM CST) and end on Monday, July 21 evening?

Since tithis represent lunar energy, which is experienced locally, I want to make sure I’m aligning my observance with the correct spiritual timing for my location.

Can you please clarify how I should calculate or observe Ekadashi or other tithis when I’m outside India?