This is something I've used a few times but recent discussion on old TV shows prompted me to have another look. It's pretty simple, just an incomplete set of BBC TV and radio listings going back to the 1920s!
It lets you answer those questions like "when was Voyage to the Bottom of the Sea first shown?" To let you correlate a memory to a rough time, or that's what I use it for anyway.
One of my childhood memories, and I have no idea why this stuck with me, is being at primary school, in the changing room for PE. One of the other boys asked if I'd seen The Green Man the previous evening, which I had.
So I did a lookup and it was shown on the evening of 9th Jan 1968. The other potential candidate was a transmission in 1970, but that was an afternoon screening, definitely not that one.
So that conversation took place on the morning of Wednesday, 10th January 1968. Useless information. And yet it means something.
https://genome.ch.bbc.co.uk/fe0c92813e8447b18841d85da14567ea