Koch, 88, died of congestive heart failure in February.
He had planned out every detail of his funeral, and although the tombstone has been in place for months, an inscriber engraved the dates just a few weeks ago.
The date of birth reads Dec. 12, 1942 instead of 1924, the New York Post said.
A manager for the Trinity Church in Washington Heights noticed the error and reached out to Koch's family, the Post said.
Flynn Funeral Home and Cremation Services handled the funeral arrangements and will make the correction, the newspaper said.