At this time, most of Europe had switched to the Gregorian calendar that we use today. England still kept to the older Julian calendar, which by then had fallen 10 days behind the Gregorian.
This caused all the confusion one might imagine, and remains an occasional nightmare for the historical researcher. Samuel Pepys took the sensible step of dating his diary in both systems; Milton appears to have used both interchangeably (hence his entirely ambiguous direction to Ellwood in the play). Ellwood, so far as I can tell, stuck to the English reckoning. However, had he been intent on hiding a few days spent in the Miltons’ home prior to his imprisonment, he could have done so by silently switching calendar systems when he came to write about it. That is, of course, unlikely, but it satisfies my dramatic instinct without doing too much violence to historical propriety.
