I also found what Dr. Jane Lyons said as interesting. I have an ancestor Patrick Joseph Martin and I have been chasing him for years. I finally have some of the answers, but not all. He arrived from Frenchpark, Roscommon to New York in 1901 and was 23 ,which has him born in 1878. He returned to Ireland and came back to the US through Ellis Island in 1906 from Ballymoe and was then 25, which has him born in 1881. I find him on the 1930 census and he is now 45, which has him born in 1885. I also found his WWI Registration card and he states his date of birth as December 28, 1878. I believe this to be the true date. I am still looking for his parents from Galway, John and Bridget Martin. He had a brother Owen Martin born 1860 and a sister Mary born 1871 and I am sure there are others in between. Nancy