Yes, you will find dates in the US that will differ than the ones on irishgenealogy.ie and this is due to several reasons. The primary reason that today we are at the mercy of those who took and recorded the information as well as those who gave the information. My Great Grandfather's oldest two brothers were about three to four years younger than what you find on the irishgenealogy.ie website. Do not dismiss the dates on the irishgenealogy site because they are the church records and even though the accuracy can be indoubt here also the information is closer to the actual fact than some of the records in the US. After I found my information on the website I emailed the church secretary in Ballyferriter and I received the church record with the dates recorded. I know it's not the perfect answer but I hope it helps.