The calendar of the year 2025 is same as that of which year?

For two years to have the same calendar, the total number of odd days between them must be 0 (i.e., a multiple of 7), and both must have the same leap-year property (i.e., both ordinary or both leap). 2025 is an ordinary year. Counting odd days from 2025 onwards: 2025 (1), 2026 (1), 2027 (1), 2028 (2, leap), 2029 (1), 2030 (1). Cumulative odd days after end of 2030 = 7, which is 0 mod 7. So calendar of 2031 = calendar of 2025. Answer is 2031.