Bobby celebrates his birthday on Monday 5 June in a certain year. In the same year Pinky celebrates her birthday on 22 September. On which day of the week does Pinky's birthday fall?

Introduction / Context:
This is another frequent style of calendar question in which we know the weekday for one birthday and must find the weekday for another birthday in the same year. The calculation involves counting the intervening days, computing odd days and then moving along the weekday cycle. Practicing such problems builds strong intuition for date arithmetic and calendar reasoning.

Given Data / Assumptions:

• Bobby has his birthday on Monday 5 June in a particular year.
• Pinky has her birthday on 22 September in the same year.
• We must find the weekday for 22 September.
• Leap year status does not matter because both dates are after February.

Concept / Approach:
The approach is to determine the total number of days between 5 June and 22 September. After obtaining this number, we divide it by 7 to find the remainder. That remainder gives the number of positions by which the weekday shifts forward from Monday to reach the day for Pinky's birthday. Complete weeks do not change the weekday, so only the remainder is important.

Step-by-Step Solution:
Step 1: Determine remaining days in June after 5 June. June has 30 days, so remaining days equal 30 - 5 = 25.Step 2: Add the full months of July and August. July has 31 days and August has 31 days, giving a total of 31 + 31 = 62 days.Step 3: Add days in September up to 22 September, contributing 22 days.Step 4: Total days between the birthdays equal 25 + 62 + 22 = 109 days.Step 5: Compute 109 modulo 7. Since 7 * 15 = 105, the remainder is 4. Therefore there are 4 odd days. Starting from Monday and moving forward 4 days gives Tuesday (1), Wednesday (2), Thursday (3) and Friday (4). Thus Pinky's birthday falls on Friday.
Verification / Alternative check:
We can regard 109 as 98 plus 11. The 98 days make 14 full weeks and thus cause no net change in weekday. The remaining 11 days are equivalent to 4 odd days because 11 modulo 7 equals 4. Moving 4 days ahead from Monday once again lands on Friday, confirming the earlier calculation.

Why Other Options Are Wrong:
Saturday corresponds to a shift of 5 days from Monday, which does not match the calculated remainder of 4.Wednesday represents only a two day shift, while our computation shows that four days of shift are needed.Sunday would require a shift of 6 days from Monday or 1 day backward, both of which conflict with the remainder of 4.
Common Pitfalls:
Some students treat June as 31 days or miscount the days in September. Others may divide 109 by 7 correctly but then misinterpret the remainder when mapping it onto the weekday cycle. A clear breakdown of month lengths and careful counting along the weekday sequence prevents such mistakes.

Final Answer:
Pinky's birthday on 22 September falls on Friday.