Postpone entering time

I have a new job from Feburary. Now I have some offers but I'd like to start it later, like Oct.Nov. even Dec, if not next semester.
Because I feel if I leave this new job just after six-month recruitment, it impacts negatively.
For an engineer, an enterprise could spend six months to former you. Leaving just after the formation is not decent.

I'd like to talk with my professor to postpone the date. Is it possible?

I applied the Ph.D and this job at the same time. At that moment, I didn't know which one would succeed so I didn't give up neither of them.
I appreciate a lot my collegues and my boss, especially my boss, he accepted me and believes me. I love my current job and perhaps after Ph.D I will come back to the same enterprise, but an other branch in USA. That's why I don't want to leave an impression that I come just for profiting the resource here.

跟老板谈清楚吧，好像有的学校也有defer的选项orz