Over 2. You’ll start seeing your O-2 pay and longevity pay bump after you pass your comm date.
In 2020, it should be your O-3 pay raise and longevity bump.
After that, they start to stagger, since the 0-4 and higher rank promotions are the result of selection boards, and the actual promotion dates, hence pay raises, are usually staggered throughout the FY.
But every two years in June, you should see the longevity bump.
Most years, you’ll also see the pay tables get a little percent of cost of living raise.
Your BAH rate is also tied to your pay grade.
I have fond memories of my O-3 promotion, longevity bump and BAH raise all the same month.
The Services have the right to mess around with things if money is tight - so the above notes are generally true. Actual promotion dates can get delayed, etc.
And, in the Marine Corps, down the career road, sometimes you will see Marine classmates promote a year later than Navy classmates, because of high retention and much smaller service.