The first line in the poem below mentions that February has 2 fortnights. A fortnight is 2 weeks. So two fortnights is 4 weeks which equals 28 days. February normally has 28 days.
February, -fortnights two,-
Briefest of the months are you,
Of the winter's children last.
Why do you go by so fast?
Is it not a little strange
Once in four years you should change,
That the sun should shine and give
You another day to live?
Maybe this is only done
Since you are the smallest one;
So I make the shortest rhyme
For you, as befits your time:
You're the baby of the year,
And to me you're very dear,
Just because you bring the line,
"Will you be my Valentine?"
Written by Frank Dempster Sherman.
Read by Corrina.