Adding 6 months to dates

Hello,

Im trying to figure out if there is a formula to add 6 months from a date to another cell.

What I have is training that occurs twice a year every 4-6 months for 2 years. As long as training gets done twice a year but doesnt exceed 6 months. So D2 being training #1, E2 being training #2, F2=#3, and G2=#4 and H2 should show the next date (6 months later) when the next training course is. D2-G2 will only be entered when the actual training has been completed. I want H2 to only show the next upcoming training as you fill in D2, E2, F2, and G2. Meaning H2 should show 6 months after D2 gets filled. Then show 6 months later once E2 gets filled and so on. I can only get it to show one date at a time. I want it to show without having to manually change the formula for the next column. this is the formula I have now
=IF(OR(D2=0),"",DATE(YEAR(F2),MONTH(F2)+6,DAY(F2))). I want to somehow show that if D2 is entered then nothing goes into H2, if D2 is entered then 6 months is added to H2, if D2 and E2 are entered then H2 to add 6 months from E2, and so on. Is this possibe?