Nasir celebrates his birthday on Thursday 18 May in a particular year. In the same year Rehan celebrates his birthday on 19 August. On which day of the week does Rehan's birthday fall?

Introduction / Context:
This problem is another example of weekday calculation within the same year when the weekday of one date is known. It checks the ability to correctly handle the lengths of different months and to use the idea of odd days, which is the remainder when total days are divided by 7. Mastery of this technique greatly simplifies many calendar questions in competitive exams.

Given Data / Assumptions:

• Nasir has his birthday on Thursday 18 May in a given year.
• Rehan has his birthday on 19 August in the same year.
• The task is to find the weekday for 19 August.
• Leap year status is irrelevant here because February is earlier in the year than both dates.

Concept / Approach:
We calculate the number of days between 18 May and 19 August, then reduce this count modulo 7 to obtain the number of odd days. Every complete set of 7 days is a full week and does not change the weekday. The remainder tells us how many steps forward we must move from Thursday to get the weekday of Rehan's birthday.

Step-by-Step Solution:
Step 1: Find remaining days in May after 18 May. May has 31 days, so remaining days are 31 - 18 = 13.Step 2: Add full months between June and July. June has 30 days and July has 31 days. Therefore days in these months total 30 + 31 = 61.Step 3: Add days in August up to 19 August, which gives 19 days.Step 4: Total days between the birthdays equals 13 + 61 + 19 = 93 days.Step 5: Compute 93 modulo 7. Since 7 * 13 = 91, the remainder is 2. Thus there are 2 odd days between the two dates. Starting from Thursday and moving 2 days forward gives Friday (1) and Saturday (2). Hence Rehan's birthday falls on Saturday.
Verification / Alternative check:
We can cross verify by noting that adding 14 days or 21 days to a date keeps the weekday the same, because each is a multiple of 7. Subtracting 91 days from 93 leaves 2 extra days, which means the weekday must move forward by exactly two positions in the weekly cycle. This argument matches our previous calculation and confirms that the correct answer is Saturday.

Why Other Options Are Wrong:
Wednesday corresponds to a shift of six days backwards or one day forwards from Thursday, which does not match the two day shift indicated by the odd days.Friday represents a shift of a single day from Thursday, which again conflicts with the remainder of 2.Thursday would be correct only if the number of days between the birthdays were a multiple of 7, which 93 is not.
Common Pitfalls:
Typical errors include forgetting that June has 30 days, wrongly assuming it has 31, or misreading 19 August as 18 August. Some candidates also confuse the direction of movement and subtract the remainder instead of adding it. Writing out the months and their day counts clearly keeps the thought process structured and avoids these mistakes.

Final Answer:
Rehan's birthday on 19 August falls on Saturday.