I just recently received a job offer (yay) but I'm unsure what should be filled in the blank lines of this part from my job offer.
If signing today I would put:
Rights this 3rd day of March, 2016
Edited: For anyone like me who thought "in witness whereof" means a separate person needs to witness the document, that is not the case. It is just a legal archaism that is almost meaningless. I based my answer on an unreliable webpage. Thanks to Pete for pointing out my error.
I'm not sure, but I think you should not fill in those lines. "IN WITNESS WHEREOF" means you need to have a witness sign this section, perhaps a notary public with a seal. The witness will fill in the date when they sign.
That being said, if
your employer hasn't said anything about needing a witness for this contract you aren't sure how to fill out something in your employment contract, ask them what to do.