In the Library Of Congress web page there is this section:
How to Pre-Register Online
It is possible to pre-register online by completing a simple Web form (this can be done up to two weeks prior to visiting the Library of Congress in person). You will still need to report to the Reader Registration Station and present your valid identification. Once your ID has been verified, Library staff will take an identification photo, have you provide a digitized signature, and give you your card.
In this example, what does "up to two weeks prior to visiting the library" mean?
Does it mean that, if I am heading to the library on the 15th of March, should I do the pre-registration between 1st to 15th of March, or does that means that I need to do it before 1st of March?