National Say Something Nice Day (1 June)

Estabished 2006 by "a group of people in South Carolina".
"The prime mover was Mitch Carnell, president of the Charleston Speech and Hearing Center, and the author of several books on communication, including _Say Something Nice: Be a Lifter @ Work_ (2012). Other supporters...included the South Baptist Convention and the Charleston-Atlantic Presbytery, and the day was officially proclaimed by the mayor of North Charleston."
Not much uptake in the rest of the world, apparently.
Crystal comments on the word "lifter" in this sense.
First recorded usage:
But thou, O Lord, art my defender : thou art my worship, and the lifter up of my head." (Psalm 3:3, Coverdale translation, 1535)
Some 17th century writer says that music is "a lifter of Dead, Drowsie and Melancholly Spirits."