If 6th March, 2005 is Monday, what was the day of the week on 6th March, 2004?

To find the day of the week on 6th March, 2004, we need to go back in time from 6th March, 2005.

1. 6th March, 2005 is a Monday.

2. We know that 2004 was a leap year. Therefore, February had 29 days.

3. From 6th March, 2005 to 6th March, 2004, we have 1 year minus 1 day (because we're not counting the start day).

4. In a non-leap year, there are 365 days, which is 1 more than a multiple of 7 (364), so it's 1 day of the week. But 2004 was a leap year, so it had 366 days, which is 2 more than a multiple of 7.

5. Therefore, if we go back 2 days of the week from Monday, we get Saturday.

So, the day of the week on 6th March, 2004 was Saturday.