The wrong date is on the tear off form of

I94. When you leave the country, I need to surrender this piece. When you reenter the us, you will get a new one. Practically, you don't have to anything under this scenario.

When it comes to how you can get back to the states from Canada, ask your boss to write a letter to explain what had happened. You can give a try at the us consulate over there. However, my recommendation is to come back to the states without applying a visa (but still with the letter though)

In the end, what you are going to do is your call. I personally don't see it's a big deal. good luck