Here's another one.
When the first year on Pick of the Pops (Radio 2, Paul Gambaccini, Saturday 13:00 - basically old top 20s) is within your teenage years.
They have two charts, one per hour, separated by 10-20 years typically. The first hour is the oldest chart.
It really seems not long ago at all, perhaps only 5 years, when the first year was usually either before I was born or in the first few years of my life, and the second year within either my teens or early 20s, so it looks like there has been a change of policy with what years are selected, rather than it just being the passage of time.