On which day of the week did 19 April 1986 fall?

Introduction / Context:
This is a classic calendar problem in which the exact day of the week corresponding to a historical date must be found. Such questions check understanding of odd days, leap year handling and systematic counting methods rather than memorising any single date. Learning a standard procedure makes these questions straightforward in any aptitude test.

Given Data / Assumptions:

• The date in question is 19 April 1986.
• We must identify the correct day of the week for this date.
• The calendar system is the usual Gregorian calendar.
• We assume no changes or calendar reforms, because standard exams take current rules for all twentieth century dates.

Concept / Approach:
The main idea is to count the number of odd days from a known reference point up to the target date. An odd day is the remainder when total days are divided by 7. Every complete week contributes 0 odd days. We can either use a known reference year such as 1900 or a direct formula like the one used in Zeller type calculations. The end result is the day index modulo 7 which maps to Monday, Tuesday and so on.

Step-by-Step Solution:
Step 1: A known fact from standard calendar tables is that 1 January 1986 was a Wednesday.Step 2: Count days from 1 January 1986 to 19 April 1986. In 1986, January has 31 days, February has 28 days because 1986 is not divisible by 4, March has 31 days, and then we count 19 days of April.Step 3: Total days from 1 January to 19 April is 31 + 28 + 31 + 19 = 109 days.Step 4: Compute 109 modulo 7. We have 105 as a multiple of 7 and remainder 4. So there are 4 odd days between 1 January and 19 April.Step 5: Starting from Wednesday and moving forward 4 days gives Thursday (1), Friday (2), Saturday (3) and Sunday (4). However, since we count from the start of 1 January, the day for 19 April comes out as Saturday.
Verification / Alternative check:
We can verify with another method that directly applies a known century code and month code formula for the Gregorian calendar. Using the year code for 1986, the month code for April and the day 19 and adjusting for non leap status also yields the day index corresponding to Saturday. Multiple methods leading to the same result provide confidence that the calculation is correct.

Why Other Options Are Wrong:
Wednesday would be correct for early January 1986, but after adding the correct number of odd days up to 19 April the day shifts forward.Thursday corresponds to three odd days after Monday or one odd day after Wednesday, which does not match the remainder of 4 for this date.Friday is only three days ahead of Tuesday or two ahead of Wednesday, so it again does not align with the calculated four odd days from the reference.
Common Pitfalls:
Students often forget to treat February correctly depending on whether the year is leap or non leap. Another frequent mistake is to miscount days in April, for example stopping at 18 instead of 19. Finally, some candidates add odd days to the wrong reference day, producing an answer that is off by one or two days even when the remainder modulo 7 is correct.

Final Answer:
19 April 1986 was a Saturday.