In some hymnals, the editors noted that a hymn's author is unknown to them, and so this artificial "person" entry is used to reflect that fact. Obviously, the hymns attributed to "Author Unknown" "Unknown" or "Anonymous" could have been written by many people over a span of many centuries. Go to person page >
Very likely not by Charles Wesley. None of the stanzas found in a search of Wesley's poetry at Duke University (1); nor are any of the stanzas in Osborn 1868-1872 (2) nor Kimbrough 2017 (3). First appearance of the hymn is in Coke and Asbury 1790 (4).
(2) Osborn, George. 1868-1872. The poetical works of John and Charles Wesley: Reprinted from the originals, with the last corrections of the authors; Together with the poems of Charles Wesley, not before published. London: Wesleyan-Methodist Conference Office. Volume 1, 1868. Volume 2, 1869. Volume 3, 1869. Volume 4, 1869. Volume 5, 1869. Volume 6, 1870. Volume 7, 1870. Volume 8, 1870. Volume 9, 1870. Volume 10, 1871. Volume 11, 1871. Volume 12, 1871. Volume 13, 1872.
(3) Kimbrough, S T, Jr. 2017. Alphabetical index to the first lines of all stanzas of poetry by John and Charles Wesley. Eugene, OR: Pickwick.
(4) Coke, Thomas, and Francis Asbury. 1790. Pocket hymn-book, designed as a constant companion to the pious, Eleventh Edition. Philadelphia, Pennsylvania: Pritchard and Hall.
Harmonia Americana: containing a concise introduction to the grounds of music; with a variety of airs, suitable fore divine worship and the use of musical societies; consisting of three and four parts #85a
Display Title: All Hail! Happy DayFirst Line: All hail! happy dayTune Title: SANTA CLARITAAuthor: Charles Wesley, 1707-1788Meter: 188.8.131.52Source: A Pocket Hymn Book (Philadelphia: Pirchard & Hall, 1788)