If 15th of February of leap year falls 3 days following Friday, what day of…

A ‘date is N days after/before a reference weekday’ problem is solved with modular arithmetic on the 7-day week: shift the reference weekday forward or backward by N (taking N mod 7), and carry a known weekday to any other date by counting the number of days between the two dates and reducing that count mod 7.

Applying this: 15 February is 3 days after Friday, and 10 March follows 24 days later in the same leap year.

1. Friday + 3 days = Monday, so 15 February (a leap year) is a Monday.

2. The leap year's February has 29 days, so from 15 February to 10 March is (29 − 15) + 10 = 14 + 10 = 24 days.

3. 24 mod 7 = 3, so 10 March = Monday + 3 days = Thursday.

Cross-check: listing every Monday from 15 February onward in that leap year gives 15, 22, 29 February and 7, 14 March — 10 March is 3 days after the Monday of 7 March, confirming Thursday. The record's own Hindi wording states the 15th falls “शुक्रवार के 3 दिन बाद” (3 days after Friday), which matches this reading, not an alternate reading sometimes used for similarly worded puzzles online that instead treats the gap as running from the 15th to Friday (18 February being Friday) — that alternate reading lands on a different offered option.

So 10 March falls on a Thursday; the previously saved key does not match the question's wording under either reading.