The calendar for the year 2025 is same for

A calendar repeats when the total number of odd days between the years sums to 0 (mod 7) and both years start on the same day of the week with same leap year status. 2025 is a non-leap year starting on Wednesday. Counting odd days from 2025: 2025(1) + 2026(1) + 2027(1) + 2028(2, leap) + 2029(1) + 2030(1) = 7 ≡ 0 odd days by end of 2030, so 2031 starts the same day as 2025. Also 2031 is a non-leap year like 2025. Hence the calendar of 2025 repeats in 2031.