http://www.infoplease.com/spot/gregorian1.html This URL explains the history of the Gregorian Calendar that we use compared to the earlier Julian Calendar (for dates prior to 1582) 1583 is the first full year of the Gregorian calendar. 1753 was the first full year in which the U.S. (then a British colony) began using the Gregorian calendar. Be aware that dates on US documents prior to 1753 were based on the Julian Calendar. http://www.infoplease.com/calendar.php This URL is a perpetual calendar. http://www.assa.org.au/edm.html This URL is a method for dating Easter Sunday. Weddings in German-Bohemia generally would not take place during Lent or Advent. When a date of marriage is unknown, this data will help to establish the "date-windows" within a given year that may produce a record. It may be a good idea to find out if the bridegroom served as a soldier. He could not marry legally while on active duty so the record of a legal marriage would have to be after he mustered out. A legal marriage required a marriage license and a civil ceremony. Active duty common soldiers could not get the license. Some married with a religious ceremony while on active duty but all children were considered illegitimate UNTIL the couple were able to get the license and go through the civil ceremony. (Some church records will show a change in status from illegitimate to legitimate for some ancestor's children.)