Calendar:

1. Q: If 1st January 2025 is Wednesday, what day is 1st January 2026?
   Answer: Thursday (2025 is not a leap year → +1 day). 

2. Q: How many odd days are there in 100 years?
   Answer: 5 odd days (since 100 years = 76 ordinary years + 24 leap years → 36500 + 24 = 36524 days → 5 odd days).

3. Q: How many odd days are there in 400 years?
   Answer: 0 odd days (400 years is a complete cycle).

4. Q: If today is Monday, what day will it be after 10 days?
   Answer: Thursday (10 ÷ 7 = 1 week + 3 days → Monday + 3 = Thursday).

5. Q: If 15th August 1947 was Friday, what day was 15th August 1948?
   Answer: Sunday (1948 is a leap year → +2 days).

6. Q: How many days are there in 200 years?
   Answer: 200 × 365 + 48 leap days = 73048 days. 

7. Q: If 1st March 2024 is Friday, what day is 1st March 2025?
   Answer: Saturday (2024 is leap year → +2 days).

8. Q: If 26th January 1950 was Thursday, what day was 26th January 1951?
   Answer: Friday (1950 is not leap year → +1 day).

9. Q: If 1st January 2000 was Saturday, what day was 1st January 2001?
   Answer: Monday (2000 is leap year → +2 days).

10. Q: How many odd days are there in 250 years?
    Answer: 3 odd days.

11. Q: If 2nd October 1869 was Saturday, what day was 2nd October 1870?
    Answer: Sunday (1870 is not leap year → +1 day). 

12. Q: If 1st January 2020 was Wednesday, what day was 31st December 2020?
    Answer: Thursday (2020 is leap year → +2 days → 366 days → 52 weeks + 2 days).

13. Q: If 1st January 2022 was Saturday, what day was 1st January 2023?
    Answer: Sunday (2022 not leap → +1 day).

14. Q: If 1st January 2024 was Monday, what day was 31st December 2024?
    Answer: Tuesday (2024 leap year → 366 days → +2 days).

15. Q: If 1st January 1901 was Tuesday, what day was 1st January 2001?
    Answer: Monday (100 years → 5 odd days → Tuesday + 5 = Sunday, but 2000 leap → +1 → Monday).

16. Q: How many odd days are there in 800 years?
    Answer: 0 odd days (2 × 400 cycle). 

17. Q: If 1st January 2025 is Wednesday, what day is 15th August 2025?
    Answer: Friday (count days from Jan 1 to Aug 15).

18. Q: If 1st January 2026 is Thursday, what day is 31st December 2026?
    Answer: Thursday (2026 not leap → 365 days → +1 day → Thursday + 1 = Friday, but Dec 31 is same day as Jan 1 → Thursday).

19. Q: If 1st January 2028 is Saturday, what day is 1st January 2029?
    Answer: Monday (2028 leap → +2 days).

20. Q: If 1st January 2100 is Friday, what day is 1st January 2101?
    Answer: Saturday (2100 not leap → +1 day).