Does this month start on a Monday?

Excel, 44 34 23 19 18 bytes


-11 thanks to Adam and -4 thanks to Shazback

-1 thanks to this

Original Answer


Ensure that the year is placed in cell A2 and the month in A3.

:( Crossed out 44 is still 44.

Ruby, 26 24 bytes


Try it online!

You'll never guess what this does.

Edit: -2 bytes from Dingus.

Bash + GNU utilities, 25 22 19 bytes

date -d$1-1|grep ^M

Try it online!

Or verify the test cases online.

The input is passed as an argument in the format year-month, and the output is the exit code (0 for truthy, 1 for falsey, as usual).