Will This Hurt My Career

Hi
I got hard copy of offer letter and signed the acceptance letter from a company, with an overlapping joining date with my releiving date from my current organization.
I have already informed the HR, and she say, that will be fine, I could join on the next day. But I am not sure, what will be considered as the Joining date for any future references, the one on offer letter or the day I join.
I don't want to have an overlapping Joining and Relieving date

Dear Saurabh,
That won't be much of a problem,as it will be considered from the day you are actually considered working and you will be paid for that...
Therefore,it won't overlap.
Wish you all the best for your job.
Regards
MK

So, is it, the day i start actually working for them will be considered as the date of joining, irrespective of the date in offer letter.

Hi Saurabh...
Yes, the first day of your physical presence will be your date of joining in the new company.....the date on offer letter just connotes the date it has been issued.
Hope it clarifies your query...
regards,