Neither is this the first time a census has been wrong. People gave the information. Proof that someone was someone particular was never called into play.
When they were small, my mother (1923-2005) and my Aunt (91 yrs old) both lived with Grandma Emma and Grampa Cully.Also, we visited with many of their cousins through the years.There is no doubt that the date on the tombstone is correct.
The census seems to be wrong.Though no one seems to know the story, or at least no one is saying...
Emma was born in 1849. In the 1860 census, she was 11. In 1870, as your post says, she was 21. When Zaccheus died inOctober, she may NOT have yet been 21.No guardian was appointed. Perhaps they let the gov't people just think he was still around!
My aunts and my mother worked on their genealogy together, and none had a birthday for Grandma Emma.
S Parker (I think) said she had the estate papers for Zaccheus. I do not, but I wish I did. I know his will was dated 1867.