Q. My great-great-grandfather died in July of 1900, but he’s still in the 1900 census. Was there a “cutoff” as to when people would or wouldn’t be recorded?
 
A. Yes, there was. Counting all the people in the United States took months, so for each census, the government established an official census date. No matter when he stopped by a particular house, each census taker was supposed to record births, deaths, ages and other information as of that date.
 
So if your great-grandfather was alive on June 1, 1900—the census date for the 1900 census—the census taker wrote him down, even if your ancestor had passed away by the time the census taker arrived in July. (You can find the date the census taker stopped by at the top of the 1900 schedule.)
 
Of course, census takers didn’t always follow their instructions exactly, and a household member could have provided incorrect information, so your census research may reveal wrong ages or people who shouldn’t have made the "cutoff." Look for other records to back up the information you find in the census.
 
Here are the official dates for US censuses:

• 1790: August 2
• 1800: August 4
• 1810: August 6
• 1820: August 7
• 1830 to 1880: June 1
• 1890: June 2
• 1900: June 1
• 1910: April 15
• 1920: January 1
• 1930-2010: April 1