Is it possible to declare double majors at separate time? For example, you declare English as your major during freshmen year then you declare psychology as your second major during Junior year making it double majors.
Depends on the school. At mine you need to have a certain number of classes done in each major before declaring the double, so it depends on if you choose to declare both majors at the same time or to start in one then add the other. For what it’s worth, I started as linguistics and added computer science between sophomore and junior year, and at my school most people are juniors when they officially declare double majors.
Your school’s course catalog should mention the process for your specific school.
As @PhantomVirgo says, it depends on the school, but in many schools you can add a major/minor right up to nearly the end- if you have done enough of the coursework that you can feasibly finish it before graduation.
It’s not uncommon (especially with minors in related fields or with subjects that you really enjoy) to find that adding just a few classes to what you have already taken is enough for it to be a major. For example, many physics majors end up with a math double major or minor.
Note that even if your college has a policy that says you can do it, it is almost always at the discretion of the department. As a random example, I know an English department that pretty much vetoes all double majors where they are asked after the first semester of sophomore year.