Century-year endings — Which weekday can be the last day (31 December) of a century year?

Introduction / Context:Century years (…1700, 1800, 1900, 2000, …) have distinctive leap-year behavior: only years divisible by 400 are leap years. This shapes which weekdays can occur on year-end dates.

Given Data / Assumptions:

• We consider Gregorian calendar rules.
• “Last day of a century” means 31 December in a year ending with 00.

Concept / Approach:Across centuries, weekday patterns cycle. For example: 1700-12-31, 1800-12-31, 1900-12-31, 2000-12-31 are known benchmarks generating allowable weekdays. Non-400 centuries shift differently than 400-multiples.

Step-by-Step Solution:

Verification / Alternative check:Day-counting modulo 7 over 100-year spans shows non-400 centuries shift by +5 weekdays; 400-multiples net a +6 shift within that block, yielding the observed set.

Why Other Options Are Wrong:

• Tuesday/Thursday/Saturday do not occur as the last day of century years under Gregorian patterns illustrated above.

Common Pitfalls:

• Assuming every 100th year is a leap year (not true unless divisible by 400).

Final Answer:Friday