Image: Thomas Percy is reading a letter
Text: 1604 30/9th May/June
My Dear Thomas
The dates at that time weren’t yet the current dates we have. Nor was the New Year in January. That changed when the UK went fully into Gregorian rather than the Julian calendar. But some people and sites used both at the same time, especially in correspondence. If you go to the OXO building in London, you can see an example on a stone on the building below it.