Determines whether the publish date of the current post in the loop is different
from the publish date of the previous post in the loop.

For more information on this and similar theme functions, check out
the {@link Conditional Tags} article in the Theme Developer Handbook.

function is_new_day() {
	global $currentday, $previousday;

	if ( $currentday !== $previousday ) {
		return 1;
	} else {
		return 0;
	}
}