Who wrote "Desiderata" and when?
Here's the simple truth. Max Ehrmann wrote "Desiderata" in the years 1921-1927. He registered it for copyright in the U.S. Copyright Office in January, 1927, as "Go Placidly Amid the Noise and Haste," later changing its title to "Desiderata." He published the poem through his sole proprietorship, Indiana Publishing Company. Between 1927 and beginning at least in the late 1950s, some copies of "Desiderata" were making their way around the country without authorship attribution. That could have happened many different ways and for many different reasons, having to do or not having to do with Max Ehrmann himself (remember that he died at age 72 in 1945).
In 1959, it was distributed at a church and in a nationally-distributed church magazine without author attribution, followed in the mid 1960s by publication in an Adlai Stevenson Christmas card without author attribution, followed by a New York Times article concerning the Stevenson Christmas card wherein the prose poem was described but with no author attribution. On top of all that, the 1959 church distribution was on note paper with a headline that read "Old St. Paul's Church, Baltimore, 1692 A.D," leading to the completely erroneous notion that "Desiderata" was found on a church wall in Baltimore in 1692 and that its author was anonymous. Desiderata The Book contains an entire chapter chronicling all this and destroying the myth. There is absolutely no doubt that Max Ehrmann wrote "Desiderata" circa 1927.