h1b visa stamping date


During H4 Interview, people are usually asked what is the Visa Stamping date for your spouse.

In my case my spouse got his visa stamped on the passport on 22nd August 2012 from company A, His I-797 was valid from 1st Oct 2012 to Sep 2015. He then moved to employer-B in India. His visa was then transferred to new employer and he got a new I-797 which was valid from march 2014-mar-2015.In Feb 2015 he changed his employer in US to employer C. After H1B transfer, New I-797 was issued which is valid from Feb-2015 to Jan-2016.

could you please confirm what will be the visa stamping date in this case.