I was recently researching a man who had married about 1840.  His wife had died within twenty years of their marriage, and he married again.  In the 1900 census, one of the questions is the birth year, and one is how long the marriage has been.  When the man and his second wife were asked these questions, a rather large mistake was made.  In the census, the man gave his birth date correctly, and then the number of total years he had been married – his first wife plus his second wife!  Then, when the woman was asked, she gave her birth date correctly, and the same number of years that her husband had given.  Of course, this was incorrect – by the wife’s birth date she was 10 when she married!

So, be careful!  Those dates may not be correct!