Lyric discussion by Jenezzy 

Cover art for Ruby Tuesday lyrics by Franco Battiato

It has one obvious meaning and one that could be a different interpretation:

1) He's singing about a girl called Ruby (who left on a tuesday) because she wanted to be free and didn't want a 'name hung' (label) on her and that he's going to miss.

2) He's singing about a tuesday when Ruby hung herself hence all the death hints (eg, dying all the time; hang a name) and absence (e.g missing you and yesterday doesn't matter if its gone) and, in death, she's free