It would be off-topic because peeving disguised as a question has been off-topic from day one. And I might add that the way your question is worded right now, it does not even attempt to pretend to know what a disguise is.
As far as I understand from day one means since the very beginning, but, in English, even in day-by-day speech, is it normal to say from day one? And what part of speech is 'day' in that fragment? Adjective?