"Mr Reginald Peacock's Day" is a 1920 short story by Katherine Mansfield. It was first published in the New Age on 14 June 1917, and later reprinted in Bliss and Other Stories.
Reginald is woken up by his wife for breakfast. He is irritated by his wife who is very polite with him. He has a bath, sings for a bit and fathoms he could be an opera singer.