When do I put my two weeks notice in? Do I need to do it a week before my two weeks or should I send it now?

Just a few days before you want to give 2 weeks notice is when I would turn it in.

Technically you don't need to turn it in any earlier than your final two weeks. However, if this is an employer you have enjoyed working for, I would suggest giving as much notice as possible. That way they are caught off guard, have time to fill your vacant position and you won't have burnt your bridges. Also depending on whether or not the company will want you to continue working until your last day. My current employer, will not let someone back on site once their two weeks has been posted. Hope that helps.

In most cases in the U.S., "two weeks notice" has no legal meaning.

If your company will want to keep you working for your last two weeks, then I would want my 2 weeks to end on the last day of a pay period. But note: In the U.S. (unless there are some unions or state laws at work), an employer is not obligated to employ you through those two weeks. Your boss could show you the door right when you submit your notice, and pay you only through that day or even hour! (Bring a box to work to pack your things!)

A few things to consider. Do you anticipate that, after giving your notice, your current employer will ask you to leave immediately? If so, will your new employer let you start earlier than your scheduled start date? If would advise truning in your notice either on Friday, September 14th or the next Monday, the 17th.