Keep in mind all timestamps are recorded in EST US Eastern Standard Time.
Can you submit on deadline day. Can you submit on the day of a deadline. Some schools have a preferred deadline which is before the actual deadline. Deadline means this day at the latest.
Contact your financial aid administrator or your state agency. Feel free to hand it in today but it will be considered late on October 1st. For priority consideration submit your FAFSA form by May 1 2021.
Can you submit applications after the deadline. Unless otherwise stated electronic applications are due by midnight of the deadline day not the midnight before it and snail-mail applications rare these days must be postmarked by the deadline day. Though the odds of being considered decreases significantly sending in your resume may still pave a path to an interview.
You can give it to your professor at 1159 Pm as long as its the 15th. For mailed applications there are two options and exactly one of. Even if its after the official Regular Decision deadline some colleges will still accept your application.
Here is an example. April 15 2021 by midnight CT. You can give it to your professor at 1159 Pm as long as its the 15th.
Frankly most colleges will look the other way if an application is a day. Most commonly the deadline is inclusive ie January 15 means that the deadline is at some moment during January 15. Once it hits 1200 its the 16th and late.