How many months have 31 days?

In my Earth Science class, I just finished teaching about phases of the moon. Trying to predict the date of the 1st quarter or full moon requires you to know how many days each month has.
I thought it may be helpful to show two easy methods to memorize how many days each month of the year has.

Method number to remember the months of the year is using the knuckles on your hand

Start with the knuckle closest to your thumb and this knuckle will be January and the space in between knuckles will represent  February then March, April, May, June, July, then for August you can start on your next hand or start over September October, November, December
All of the Months on the Knuckle have 31 days.
They are January, March, May, July, August, October, December
The months in the space between knuckles have 30 days except for February which has 28 days.

Another method you can use to memorize the days is this poem.

30 days has September,
April, June, and November.
When short February's done
All the rest have thirty-one

I actually use the poem to remember September has 30 days and February has 28 days combined with my knuckles.