Nobody was born in Derry between September 3 and 13 in 1752. In fact nobody was born on any of those dates anywhere in these islands. Those dates just didn’t exist. People went to bed on Wednesday September 2 and awoke next morning on Thursday September 14. How come?

Well, in 46BC Julius Caesar had authorised a new calendar. But it miscalculated the sun’s year by 11 minutes - which added up to one full unmeasured day every 128 years. So what? Well that gradually moved the date of Easter and the seasons away from their actual timing by the sun.

So in February 1582 Pope Gregory XIII introduced a corrected calendar based on the actual c365¼-day year of the sun, making 11 months of 30 and 31 days, and February having only 28 days. Then every four years that annual ¼ day catches up and gives February an extra 29th day.

Various countries ignored Pope Gregory’s new calendar and continued with Julius’s old calendar. But in September 1752 Britain and her Empire adopted the Gregorian calendar and skipped 11 days to catch up with it.

placeholder image — 30 days has September? Not in 1752.

There are many different calendars in the world. But the Gregorian calendar is now almost universally used.

For its Year Zero, our Gregorian calendar takes the estimated date of the birth of Jesus - 2,026 years ago. And if you wanted a calendar based on the existence of our human species, Homo Sapiens (=”intelligent man”), then today would be roughly Friday 11 September 302,026.