H1B validity.

[nshaily]

I got my H1B visa extension for three years on basis of approved I-140.

Here is the situation and question.

A- My current H1B visa will experis on 30th September and new VISA is starting from 2nd October. Somehow my employer missed the starting date October 1st.

Is it ok if I am here on October 1st (My current H1B visa will experis on 30th September and new H1B start on 2nd October).

Will this give me any trouble in my green card process.

 

[GotPR?]

To be strict, you'll be on illegal presence for 1 day as I-94 dictates legal ground of stay. I'd say it won't be a serious problem, but if you are asked about your violation for visa term on future visa/GC applications, you need to answer YES.
It is not comfortable to tell immigration officer/consulate officer that you had experience of overstay so that it's better to fix. Please ask lawyer if he can ask ammendment.