The date the PTO receives a particular patent application is a very important date to remember. Think of it as the application's birth date.

If the application is allowed to patent, the date protection begins will be the filing date of the application, not the date the application was allowed or accepted to become a patent (as you might expect). The major reason for this is that others may send in applications during the "patent pending" time period.

In situations where a number of patents covering the same invention begin flowing in, the first filed application will usually gain the patent. The length of the patent term is cut a little short by using the filing date, but it is usually more of a benefit to the applicant than a loss.

By using the filing date, applicants may begin marketing the product before the application issues without fear of losing the idea to someone else.

Here's an example:

Joe files his patent application July 1, 2013 and his patent is finally granted on October 15, 2014. The filing date of Joe's application is July 1, 2013. The subject matter will have been protected ever since July 1, 2013. If anyone else sends in a patent application claiming the same exact subject matter after that date, the PTO will likely reject it.