Can anniversaries help us all know more about history?

2019 has been quite a year for historical anniversaries – Peterloo 200, D-Day 75, Monte Cassino 75, Women MPs 100 years, Apollo Moon Landings 50 years and all following on the tail of four years of the First World War centenary – and that is not counting the anniversaries that are now entrenched as a regular feature for every year – such as Bonfire Night. Furthermore the anniversaries for this year are not yet over, so what does marking an anniversary give us?