Ding-A-Ling-Day is a lovely concept. The idea is to call someone you have not heard from in a while. The ding-a-ling is from the sound of a telephone bell.
I got entirely the wrong idea when I first read it, because I was remembering the hit song ‘My Ding-a-Ling’. Are you old enough to recall Chuck Berry singing his rather risqué novelty song in 1972 – and the fuss it caused?