What day should i ask him to my school dance?? please help!?

[SophomoreGirl92]

okay soo most of my questions have been about this guy who is a senior in highschool and i like him, but im not sure he likes me back. we're good friends so i dont think he'll say no, but at the same time i highly doubt he'll say yes. but im gonna ask him anyways.
but im having trouble deciding what day to call him and ask him, because i dont want to call to early and sound desperate, and i dont want to call him too late because he'll probably get plans.
so here are the dates:
My School Dance: May 24th
days to call him: April 19th; April 26th; May 3rd. and MAYBE May 10th-but i feel that might be too close to the date of the dance.
incase you havent figured it out, ive never asked anyone to be my date for something and because hes a senior im a little more nervous than usual.
please help me!!!
(ill pick by the date by the majority of votes)
ohh and my school dance is considered to be prom. its our only dance the entire yr, and because its such a small school 9th-12th grd can go. thats why me, a sophomore, is the onoe asking the senior haha