What was the day on 31 March 1931?

\(\frac{Date + Month\;code + Century\;code + Century\;upper\;year + Quotient\;of\;\frac{upper\;year}{4}}{7}\)

⇒ \(\frac{31 + 3 + 0 + 31 + 7}{7}\) ⇒ \(\frac{72}{7}\) = 2 Remainder

2 Remainder → Tuesday.

Note:     

Code for      Mon – 1      Tues – 2      Wed – 3      Thurs – 4

                   Fri – 5         Sat ­­– 6        Sun – 0

Code for      Jan – 0        Apr – 6       July – 6       Oct – 0

                   Feb – 3       May – 1      Aug – 2       Nov – 3

                   Mar – 3       June – 4      Sep – 5       Dec – 5

Code for     

1900 is 0

2000 is 6

2100 is 4

2200 is 2

2300 is 0

2400 is 6

2500 is 4   and  Likewise