I started working in September 2009 so I wasn't working till then.

[tufguy]

I wasn't working till September of 2009.

I started working in September 2009 so I wasn't working till then.

My question is "can we use 'till then' like this for past incidents'?

 

[tedmc]

Yes, but it is not advisable to write like that.

What was the period you were not working? From which date until Sept 2009?

You started working in Sept 2009 until what date?

With information involving dates and figures as in a timeline, it is best to have them presented in a table.