"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.
He has a bath, sings for a bit and fathoms he could be an opera singer.
When he gets home he thinks his wife an ingrate for not celebrating his 'triumph', whilst it so happens that he did not even tell her he would be away for dinner.
The text is written in the modernist mode, without a set structure, and with many shifts in the narrative.