I've heard people using あした (the common one) and あす (rather uncommon) to refer to "tomorrow".
I was wondering does anyone actually uses the reading みょうにち ?
Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It only takes a minute to sign up.Sign up to join this community
I have heard it used in formal (e.g. business) contexts. I have never heard it used in casual conversations among friends or family.
This is what you might expect, because Sino-Japanese words like みょうにち do tend to have a more formal feel than native Japanese words like あした or あす, when they exist alongside each other with similar meanings.
In some parts of Tohoku, the greeting "おやすみなさい" or "また明日" is said "おみょうにづ", with is a deformation from "おみょうにち". Even though it refers to the next day, I think that "お" is the same one as in "お早う".
I can't remember whether "あした" is casually said "みょうにづ" though…
Sometimes old people do. I don't know why, but maybe they feel uncomfortable with 熟字訓読み as in あした or あす, where the portion of the pronunciation of a word does not match each kanji character.