Since yesterday till today

[tufguy]

I want to tell you what I have done "since yesterday till today" or "from yesterday until today".

Please check.

 

[emsr2d2]

I want to tell you what I've done since yesterday.
I want to tell you what I've done between yesterday and today.

I prefer the first.

 

[Charlie Bernstein]

Those are good. To me, "since yesterday" means "today," so I would say "I want to tell you what I did yesterday and today." (Or: "Let me tell you . . . .")