The end date is the date for when you want to reach your goal. The date simply gives a signal to your network that this is the date you want to have reached your goal. NB. This does not mean that the fundraiser will be removed or closed for donations. You can still receive donations after this date and your fundraiser will still be visible for everyone. You can, at any time, edit the end date of your fundraiser and it is very easy to do.
How to extend the end date?
Log into your BetterNow account and click on "My Fundraisers" in the right upper corner. Click on the fundraiser, and thereafter click "Edit Fundraiser" in the left upper corner. You can now edit all the data you previously set about your fundraiser. Just change to the date you wish, and click "Save Changes".
For more information, see here.