Question

What was the day of the week on 12th January 1979?

Answer 1

Number of odd days in (1600 + 300) years = (0 + 1) = 1
78 years = (19 leap years + 59 ordinary years)
= (38 + 59) odd days
= 97 odd days = 6 odd days
12 days of January have 5 odd days
∴∴ Total number of odd days = (1 + 6 + 5) = 5 odd days
Hence total desired day was 'Friday'