the Gregorian calendar was backdated, recalibrating the year as if it, rather than the Julian option, had always been used. Through the use of pope power, it was decreed that ten dates would be taken from October 1582 and so, in Catholic countries, October 4, 1582, was directly followed by October 15. All this does of course make historical dates a bit confusing. When the English forces landed on Île de Ré on July 12, 1627, as part of the Anglo-French War, the French forces were ready to fight back on July 22. That is, on exactly the same day. At least, for both armies, it was a Thursday.
