First day of a leap year is Wednesday, then what day of the week was it on 31st December in that year?

If 1st January, 2001 was Monday, then what day of the week was it on 31st December, 2001?

If October 10, 2023 was a Tuesday, then what day of the week was December 23, 2023?

If August 15, 2023 was a Tuesday, what day of the week was August 15, 2024?

It was Sunday on Jan 1, 2006. What was the day of the week on Jan 1, 2010?

It was Sunday on January 1, 2006. What was the day of the week on January 1, 2010?