Maybe we should all adopt Chinese weekday names: Sunday (星期日) remains same, Firstday (星期一) for Monday, Seconday (星期二) for Tuesday, Thirday (星期三) for Wednesday, Fourthday (星期四) for Thursday, Fifthday (星期五) for Friday and Sixthday (星期六) for Saturday. One-letter abbreviations would be simply S, 1 through 6.
Why downvoted? This is correct.
I believe that's how Russian names the days as well. In Hebrew and Arabic we do the same, but Sunday is First Day, Monday is Second Day, etc.