My issue date for my J-1 visa is 20th of may 2018, the start date on my Ds 2019 form (which is also stated in the visa in my passport) is 30th august 2018. Is it ok for me to enter the US on the 22nd of august? It is within the 30 day period but I am confused since it says 30th of august in the visa
It's not normal for a J-1 visa to show the DS-2019 program dates, particularly because normally the DS-2019 program dates can be changed and you can still use the same visa. Try a Google image search for "J-1 visa" and you will see that most mention only issue date and expiration date, as well as the annotation regarding whether you're subject to the 212(e) two year home residence requirement.
Normally, when the J-1 visa doesn't show the program dates, you can enter the US up to 30 days before the DS-2019 program start date. This is probably true in your case as well, but you should check with the consulate that issued the visa to be sure. Be sure to keep your program sponsor (DS-2019 issuer) informed as well.