When I looked it up, I found a list of different sorts of national chocolate days. I assume, but haven't researched it, that they were a marketing idea thought up by the UK chocolate product retail industry.
Brief growl about annual days of whatever - whilst I fully accept that some days are logically a particular date, chosen for or in remembrance of a particular event, a particular day of the month, e.g. first Thursday or whatever, makes better sense for most things.
It can be pretty horrid if someone very close to you dies and the date of their death coincides with national what-they-died-of day. I say that whilst still aware that for some, the sense that awareness of a condition is being raised may bring consolation.
Sudden giggle - I just looked up a list of national days for the coming year.
https://www.thereisadayforthat.com/countries/united-kingdom April Fool's Day launches Stress Awareness Month and National Pet Month.
This year, World Cocktail Day is the same as National Numeracy Day - are you counting how many cocktails it takes you to get drunk?
There are more to be found out there on different sites. There you go, something to stop me grumbling about special days that coincide.
