ReactJS pass wrong value in for loop

Question

This is my code:

changeDay(value){
    console.log(value)
}

for (var i = 1; i <= 31; i++) {
    rows.push(<span onClick={() => this.changeDay(i)} key={i}>{i}</span>);
}

My console print 32 per span!

I click on 1 or 2 or 3 or ..., but pass 32 to changeDay!