2031 is not a leap year. Which of these months of 2031 begins on the same day of the week as September 2031?

Explanation

1. 01

   Two months begin on the same weekday when the days between their first days form whole weeks.

2. 02

   From 1 September to 1 December: $30 + 31 + 30 = 91$ days $= 13$ weeks exactly.

3. 03

   Check the others: to 1 October is 30 days (2 odd days), to 1 November 61 days (5 odd days); June begins 92 days before September (1 odd day).