> > I'm doing it since 09/22/2014
>
> This is one of those wierd places in English where
> the verbs "to do" or "to be" combine strangely with
> tenses and idioms. I'm not so sure of the technical
> way of stating the problem,
If I'm not mistaken, the technical issue is that "I'm doing" is in the Present Progressive tense/aspect (an ongoing event in the present), which doesn't match having the past date there. "I've been doing" is in the Present Perfect Progressive tense/aspect (an event beginning in the past, but continuing into the ongoing present).
