Can I submit application on the deadline? If grad schools says the deadline is Jan. 15th, do I have to submit application before Jan. 15th? Or I can still submit on Jan. 15th?
Most commonly the deadline is inclusive, i.e., "January 15" means that the deadline is "at some moment during January 15". What does this mean can vary:


For online applications, it's usually 23:59:59.
For mailed applications, there are two options and exactly one of them is true:


either the poststamp has to be January 15;
or it has to arrive to the institution by January 15.

For applications you deliver in person, usually the opening hours of the office where you have to bring it apply.


In either case, it should be specified in the conditions.

And please remember that timezones can play a role here, and everything is in the timezone of the institution where you apply unless stated otherwise.



/From comments/

If you doubt the precise conditions, just call them or e-mail them and ask for clarification.

It will cost you less than solving any troubles afterwards.