President Barack Obama erred during a tour of London's Westminster Abbey when he signed a guest book with a date in 2008.
"It is a great privilege to commemorate our common heritage, and common sacrifice," the Obamas wrote in the guest book.
A Westminster Abbey spokesman confirmed it was President Obama who signed the incorrect date.
President Obama also placed a wreath at the Grave of the Unknown Warrior at the church, The Daily Telegraph reported. He was given a tour of Westminster Abbey from the Very Rev. Dr. John Hall.
"Here has taken place every coronation of kings and queens of England and of the United Kingdom since William I was crowned here on Christmas Day 1066."
Hall noted thousands of international visitors "including very many from the United States are welcomed" every day.