Month-to-month shift – If it is Saturday on 27 September, what day of the week will it be on 27 October of the same year?

Introduction / Context:
We seek the weekday one month later on the same day-of-month. The shift in weekday between the 27th of one month and the 27th of the next depends on the number of days between these dates, which equals the length of the intervening month (here, the remainder of September plus the first 27 days of October).

Given Data / Assumptions:

• 27 September = Saturday (given).
• September has 30 days.
• Number of days from 27 Sep to 27 Oct = 30 (because from 27 Sep to 30 Sep is 3 days, then 27 more days in October; 3 + 27 = 30).
• 30 mod 7 = 2.

Concept / Approach:
The weekday advances by the number of days modulo 7. A 30-day gap advances the weekday by 2. So add two days to Saturday.

Step-by-Step Solution:

Verification / Alternative check:
List the tail of September: 27(Sat), 28(Sun), 29(Mon), 30(Tue). Then advance 27 days into October: Tue + 27 ≡ Tue + (21 + 6) ≡ Tue + 6 = Monday. Same result.

Why Other Options Are Wrong:

• Thursday/Friday/Sunday: These correspond to +5, +6, or +1 shifts from Saturday, not +2.
• None of these: The correct weekday is listed explicitly (Monday).

Common Pitfalls:
Assuming “one month later” always advances by the same amount; the shift depends on the number of days between the two dates, which varies by month length. Always compute the actual day gap and reduce modulo 7.

Final Answer:
Monday