The realization has just hit – you're going to need to take the GRE for grad school, and it's feeling like high school all over again. You have another standardized test to squeeze into your busy schedule of classes, exams, extracurricular activities and application deadlines.

Before you get too stressed out about finding time to take the test, you should know that there are quite a few differences between the GRE and the SAT or ACT. In fact, the differences are in your favor:

- You can take the GRE almost any day of the year, and it's usually available once in the morning and once in the afternoon. This gives you a huge amount of flexibility in choosing the perfect test date. Feel like taking it on a Friday afternoon when you don't have classes? Go for it – no need to wake up super early on a Saturday this time!

- Official test scores can take up to four weeks to get to your target schools. So although you can take the test virtually any time of the year, what you really need to zero in on are the test score deadlines for each of the graduate schools where you're applying. Write down all of the deadlines, and plan to take the GRE at least five weeks before the earliest one so you won't have to worry about any late scores. But you should also give yourself plenty of buffer time before your grad school deadlines to retake the GRE in case your score isn't what you need, says Paul Bodine, founder and president of Admitify.com.

To really pin down a test date, Bodine says students should identify a date range “when your workload (academic or otherwise) is amenable to studying for the GRE. Then take the actual test when you are not stressed out about exams or other deadlines."

If you plan to take the GRE more than once, then you should try to take your last attempt at the test at least five weeks before the earliest score deadline. Just remember that you have to wait 21 days between tests and can only take the GRE a maximum of five times in the period of one year (365 days).

- GRE test scores don't expire for five years. You could technically take the test in your freshman year if you were already 100 percent sure about attending grad school right after college. But then again, you might end up waiting a year or three after graduating from college to go to grad school, depending on your career and life goals. It makes more sense to take the test in your junior or senior year so you give yourself plenty of breathing room to apply to grad school before the score expires.

- Perfect timing doesn't really matter if you haven't fully prepared yourself for the GRE. Essentially, like all other standardized tests, when you take the test should really depend on when you are prepared to take it. If you decide to go the route of applying to enter grad school the fall after you graduate from college, Bodine recommends prepping for the test in the spring or summer before your senior year, taking the test in the summer and potentially retaking it if necessary in the fall. Just remember that you'll have to wait 21 days between test dates, and that some graduate programs will require you to submit your GRE reports before the deadline for the full application.

Calculate Prep Time

How much time should you spend on getting ready for the GRE, since that will affect the timing of when you take the test? Bodine says students should aim to prep for at least two to three months. “If your GRE diagnostic score was below your target schools' median GRE by 20 points, you may need 150 to 170 hours (ballpark) of additional prep time to lift your score 20 points. So depending on how many hours you can spare per day for GRE prep, you will need to start studying seven (three hours of GRE prep a day) to 11 weeks (two hours of GRE prep a day) before your test date."

Bottom line: The moment you know that you will want to go to grad school, it's time to strategize for the GRE so you can plan ahead and build in plenty of preparation time.