Calendar and Clock — Odd Days, Finding Any Date's Weekday and the 30H − 5.5M Angle Rule

Calendar and clock is the block most students skip, and it is the one block in reasoning where the answer is fully determined. There is no interpretation, no 'best fit', no arguing with the examiner afterwards. A date has exactly one weekday and two hands have exactly one angle between them, and both come out of a formula that fits in a line.

SSC CGL and CHSL carry one or two of these in almost every shift. Railway NTPC and Group D like the counting versions. BPSC TRE-4 and CTET tuck them into mental ability. The reason they keep appearing is the same reason they are worth learning — they cannot be guessed from the options, so they separate a prepared candidate from an unprepared one in about forty seconds.

Two tools do the whole job: odd days for anything with a date in it, and 5.5 degrees per minute for anything with hands on it.

1. How many odd days are there in 100 years?

2. 15 August 1947 fell on which day of the week?

3. What is the angle between the hands of a clock at 3:40?

4. In 24 hours, how many times do the two hands of a clock form a right angle?

5. Which of the following is NOT a leap year?

6. The hands of a correct clock coincide after every —

7. 26 January 1950, the first Republic Day, fell on which day?

8. A clock seen in a mirror shows 4:20. What is the correct time?