If your project was approved by the Advisory Board, it depends on the term length that you were approved for; if your project was approved for two years, then your project end date is two years after the original Board approval date. Same for three years, five years, etc.
If your project is a directive, the project begin date is the date of the letter delivered to the ERC director informing us of the project; the end date is determined by how many years are anticipated by that project’s researchers.