This article is from the alt.usage.english FAQ, by Mark Israel firstname.lastname@example.org with numerous contributions by others.
"Desiderata" was written in 1927 by Max Ehrmann (1872-1945). In
1956, the rector of St. Paul's Church in Baltimore, Maryland, used
the poem in a collection of mimeographed inspirational material for
his congregation. Someone who subsequently printed it asserted that
it was found in Old St. Paul's Church, dated 1692. The year 1692
was the founding date of the church and has nothing to do with the
poem. See Fred D. Cavinder, "Desiderata", "TWA Ambassador", Aug.
1973, pp. 14-15.