Calendar – Relative weekday: If Monday fell on 6 March 2005, what was the day of the week on 7 March 2004?

Introduction / Context:
We compare dates across adjacent years to find the weekday. The key is whether the span includes a leap day and how many days elapse between the two dates.

Given Data / Assumptions:

• 6 Mar 2005 = Monday (given).
• Find weekday for 7 Mar 2004.
• 2004 is a leap year; however, Feb 29, 2004 occurs before March 6/7.

Concept / Approach:
From 7 Mar 2004 to 7 Mar 2005 is 365 days (leap day Feb 29, 2004 lies before Mar 7, so the span does not include an extra day). Hence from 7 Mar 2004 to 6 Mar 2005 is 364 days, a multiple of 7, so weekdays match.

Step-by-Step Solution:
1) 7 Mar 2004 → 7 Mar 2005: 365 days → weekday advances by 1.2) 6 Mar 2005 is one day earlier, so 7 Mar 2004 and 6 Mar 2005 share the same weekday.3) Since 6 Mar 2005 is Monday, 7 Mar 2004 is Monday.

Verification / Alternative check:
Use a perpetual calendar to confirm the alignment.

Why Other Options Are Wrong:
Tuesday, Friday, Sunday → do not match the computed equality.

Common Pitfalls:
Assuming leap day affects March-to-March spans in 2004; it does not for March 7 onward.

Final Answer:
Monday