Shave on Erev Rosh Hashana
The Tur (O.Ch. 581) quotes the Midrash .
"The Minhag of the world is when a person has a court case, he dresses
in black ,wraps himself in black and grows his beard etc.
The Bnei Yisroel are different. They dress in white they wrap
themselves in white and shave their beards. ומגלחין זקנם)) )*
*גילוח is shaving not trimming