Interested in Language
How Did The Phrase Happy Birthday To You Or Many Happy Returns Of The Day Start And How It Picked Up? Ever Wondered About This Most Often Used Term.
"Happy Birthday to You" [the song] is late 19th century, but there is no telling when the wish was first used.
The earliest recorded written use of the second is at the end of the eighteenth century, which probably means it was certainly in use verbally in that century.
nb - You only need a capital letter on the first word in a sentence or for proper names.