Need assistance on a Power Bi DAX on a case study !!

[Gowthami_20]

Upgrade /Promotion formula for direct up grade(Column): To be calculated

Grade(11-15) -joining date + 18 months(1st upgrade) after that every 1 year upgrade

Grade(1-10) = upgrade every 1 year

Thanks in Advance!!

[lbendlin]

Please provide sample data in usable format (not as a picture) and show the expected outcome.