Calendar – Relative weekday: Given that 4 April 1988 was a Monday, what day of the week was 6 November 1987?

Introduction / Context:
We move backward from a known weekday to an earlier date by counting intervening days and accounting for month lengths.

Given Data / Assumptions:

• 4 Apr 1988 = Monday.
• Find weekday for 6 Nov 1987.

Concept / Approach:
Count days from 6 Nov 1987 forward to 4 Apr 1988, then shift the weekday backward accordingly. Alternatively, compute each date’s weekday via a congruence and compare.

Step-by-Step Solution:
1) Using a standard weekday algorithm for both dates yields that 6 Nov 1987 is Friday.2) Consistency checks with month lengths (Nov→Dec→…→Apr) confirm the offset.

Verification / Alternative check:
Applying Zeller/Doomsday directly to 6-11-1987 returns Friday.

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

Common Pitfalls:
Off-by-one errors when crossing months and year boundaries.

Final Answer:
Friday