Most colleges that offer an Early Decision II option have a January 1 deadline, but there is some variation, so prospective ED II applicants should read Web sites carefully to find accurate information.
Note also that, if a student has already applied Regular Decision to a college before the ED II deadline but then would like to convert the RD application into an ED application, most colleges will allow this, even if it's a week (or sometimes even a couple weeks) after the ED II deadline.
For more information on the pros and cons of applying ED II, check out this earlier “Ask the Dean" column: