12 December 2023 minus 800 weeks will be
12th August 2008
The Gregorian calendar is the most widely used internationally civil calendar. It is named after Pope Gregory 13th, who introduced it in October 1582.
The Gregorian calendar is a solar calendar. A regular Gregorian year consists of 365 days, but as in the Julian calendar, in certain years, a leap year, a leap day is added to February
The months of April, June, September, and November have 30 days, while the rest have 31 days except for February, which has 28 days in a standard year, and 29 in a leap year.
For best results, please use dates after 1752 and verify any data if you are doing genealogy research.