Assistant Provident Fund Commissioner and Enforcement Officer / Accounts Officer (APFC and EO/AO) 2025 recruitment test. Transcribed from the Commission's own booklet (series A, PENA-A-PTS); answer worked out by our faculty — UPSC has published no answer key for this sitting. This question is in Part B. Answer last reviewed 25 August 2026.

If 2nd February, 2025 was Sunday, which day was it on 1st February, 2024 ?

(a)Saturday
(b)Monday
(c)Thursday
(d)Friday

Answer

Why

Correct — C, (c) Thursday. Two steps, and the second is where the leap year has to be handled. STEP 1 — move within February 2025. The 2nd of February 2025 was a Sunday, so the 1st of February 2025, being the day before, was a SATURDAY. STEP 2 — move back one year, from 1 February 2025 to 1 February 2024. Count the days in that interval: it runs from 1 February 2024 to 1 February 2025 and therefore CONTAINS 29 February 2024, because 2024 is a leap year. So the interval is 366 days, not 365. 366 = 52 × 7 + 2, so there are 2 'odd days' — two days left over after whole weeks. Going FORWARD from 1 February 2024 to 1 February 2025 advances the weekday by two. We are going backwards, so we subtract two from Saturday: Saturday − 1 = Friday, Friday − 1 = Thursday. The 1st of February 2024 was a THURSDAY. The point to be careful about. It is not enough to ask whether either year is a leap year; the question is whether 29 FEBRUARY LIES INSIDE THE INTERVAL you are counting. Here the interval starts on 1 February 2024 and ends on 1 February 2025, so 29 February 2024 is inside it and the interval is 366 days. Had the two dates been 1 March 2024 and 1 March 2025, the leap day would have fallen just before the start and the interval would have been 365 days, worth one odd day only. A check by another route. 1 February 2024 to 1 February 2025 is 366 days; 366 days after Thursday is Thursday plus 2 = Saturday, which matches step 1. And Saturday 1 February 2025 puts Sunday on the 2nd, exactly as the stem states. Every date in the question is consistent.

Why the others are wrong

(a)Saturday — Saturday is the answer to a different question — it is the day on which 1 FEBRUARY 2025 fell, which is the halfway point of this calculation. A candidate who completes step 1 and then forgets that the question asks about 2024 stops exactly here. Note that the two dates in the stem differ in BOTH the day of the month and the year, so neither can be assumed to repeat.
(b)Monday — Two days after Saturday rather than two days before it. The direction of travel is what has gone wrong: moving from an earlier date to a later one advances the weekday, so moving from 2025 back to 2024 must retard it. A useful habit is to state the direction in words before doing the arithmetic — 'going back, so subtract'.
(d)Friday — The leap-year answer: it comes from counting 365 days between the two dates, giving one odd day instead of two, so Saturday goes back only to Friday. The interval from 1 February 2024 to 1 February 2025 includes 29 February 2024 and is 366 days long. This is the single most common error in calendar questions and the option is placed here to catch it.

Concept

Calendar problems are arithmetic modulo seven. Any number of days is reduced to its remainder after dividing by seven — the 'odd days' — and only that remainder shifts the weekday. An ordinary year of 365 days has 1 odd day, since 365 = 52 × 7 + 1; a leap year of 366 days has 2. The Gregorian rule for leap years is that a year divisible by 4 is a leap year, except a century year, which must be divisible by 400: so 2000 was a leap year and 1900 was not. Longer spans use the same idea — 100 years contain 5 odd days and 400 years contain none, which is why the whole calendar repeats every 400 years. For a span between two dates, the only question that matters is how many 29 Februarys fall inside it.

One calendar item appears in most papers in this family, and it is always solvable in under a minute by the odd-days method. The examiner's usual devices are exactly the two used here: dates that differ in both day and year, so that no shortcut works, and a leap day placed just inside or just outside the interval. Recognising which of those two situations you are in is the whole difficulty. Calendar items are always solvable within a minute, and the examiner's variables are few: which dates are chosen, and where the leap day falls relative to them. Here both variables are used — the two dates differ in day of the month AND in year, so no shortcut applies, and 29 February falls inside the interval, so the span is 366 days. Deal with the two moves separately and in writing: adjust within the month first, then across the years, stating the direction of travel before subtracting. Almost every wrong answer in a calendar question is a direction error or a leap-day error.

Key facts

Odd days are the remainder after dividing a number of days by seven; only they shift the weekday.
An ordinary year has 1 odd day; a leap year has 2.
A year is a leap year if divisible by 4, except century years, which must be divisible by 400.
2024 is a leap year, so the interval from 1 February 2024 to 1 February 2025 contains 29 February 2024 and is 366 days.
366 days = 2 odd days, so the weekday advances by two across that interval.
Moving forward in time adds odd days; moving backward subtracts them.
What matters is whether 29 February falls INSIDE the interval, not whether either end-year is a leap year.
The Gregorian calendar repeats exactly every 400 years, which contain no odd days.

Study next

The odd-days method for finding the day of the week of any dateLeap year rules, including the century exceptionCounting odd days over centuries and the 400-year cycleProblems asking when a calendar year repeatsClock problems, which use the same modular arithmetic on twelve hours

Common traps

Counting 365 days across an interval that contains a 29 February.
Adding odd days when the question moves backwards in time.
Assuming the day of the month is the same at both ends when it is not.
Testing the leap year status of the end-year instead of asking where the leap day falls.

Calendar questions in EPFO papers give one known day and ask for another, usually across a year boundary chosen so that a leap day is involved. Solve them in two moves — adjust within the month, then across the years — and state the direction of travel before doing the arithmetic.

Related PYQs

No directly related past PYQ was found.

Practice

practice — not a real PYQ
If 1st March 2024 was a Friday, what day of the week was 1st March 2025 ?
- (a)Friday
- (b)Saturday
- (c)Sunday
- (d)Monday
Answer(b) Saturday
practice — not a real PYQ
How many odd days are there in an ordinary year of 365 days ?
- (a)0
- (b)1
- (c)2
- (d)3
Answer(b) 1

Why

Why the others are wrong

(a)Saturday — Saturday is the answer to a different question — it is the day on which 1 FEBRUARY 2025 fell, which is the halfway point of this calculation. A candidate who completes step 1 and then forgets that the question asks about 2024 stops exactly here. Note that the two dates in the stem differ in BOTH the day of the month and the year, so neither can be assumed to repeat.
(b)Monday — Two days after Saturday rather than two days before it. The direction of travel is what has gone wrong: moving from an earlier date to a later one advances the weekday, so moving from 2025 back to 2024 must retard it. A useful habit is to state the direction in words before doing the arithmetic — 'going back, so subtract'.
(d)Friday — The leap-year answer: it comes from counting 365 days between the two dates, giving one odd day instead of two, so Saturday goes back only to Friday. The interval from 1 February 2024 to 1 February 2025 includes 29 February 2024 and is 366 days long. This is the single most common error in calendar questions and the option is placed here to catch it.

Concept

Key facts

Odd days are the remainder after dividing a number of days by seven; only they shift the weekday.
An ordinary year has 1 odd day; a leap year has 2.
A year is a leap year if divisible by 4, except century years, which must be divisible by 400.
2024 is a leap year, so the interval from 1 February 2024 to 1 February 2025 contains 29 February 2024 and is 366 days.
366 days = 2 odd days, so the weekday advances by two across that interval.
Moving forward in time adds odd days; moving backward subtracts them.
What matters is whether 29 February falls INSIDE the interval, not whether either end-year is a leap year.
The Gregorian calendar repeats exactly every 400 years, which contain no odd days.

Study next

Common traps

Counting 365 days across an interval that contains a 29 February.
Adding odd days when the question moves backwards in time.
Assuming the day of the month is the same at both ends when it is not.
Testing the leap year status of the end-year instead of asking where the leap day falls.