If you’ve been researching for any length of time, you’ve probably run into someone who just wasn’t too concerned about giving a correct age in the records he or she left behind. And yes, it does seem to be the ladies most often. (Jane Kelly Pechin, I am thinking of you.)
Well, now we can say they were in good company. Mary Todd Lincoln was born on 13 December 1818, which for most people would mean that this is her 195th birthday. But when I went to look for her in the census we find that in 1850 when she first appears by name, where we would expect that she was 32, she has already dropped a few years and is only 28.
Moving forward ten years (at least for us mere mortals), Mary managed to only age another seven years and gives her age at 35 in the 1860 census.
Mary was traveling overseas in 1870 and 1880 so we don’t know how she would have listed her age for those enumerations, but based on these two censuses, we can only guess she would have been 42 and 49, respectively. So the next time an ancestor has you beating your head on the wall, you can take some small comfort in the fact that your ancestor wasn’t the only one who played it fast and loose with the census taker. So happy 142nd birthday Mary Todd Lincoln!
 1850 U.S. Census, Illinois, Sangamon County, population schedules, Springfield, page 120 [stamped], line 32, Abraham Lincoln household; digital image, Ancestry.com (http://search.ancestry.com/search/db.aspx?dbid=8054: accessed 13 December 2013); citing NARA microfilm M432, roll 127.
 1860 U.S. Census, Illinois, Sangamon County, population schedules, Springfield, page 140, line 16, Abraham Lincoln household; digital image, Ancestry.com (http://search.ancestry.com/search/db.aspx?dbid=7667: accessed 13 December 2013); citing NARA microfilm M653, roll 226.