How many years has Marc been an astronaut for?

To determine how many years Marc has been an astronaut, I would need to know his specific astronaut selection date or the year he began his training. Generally, astronauts can serve for several years, often starting in the early 2000s or later, but without that specific information, I cannot provide an exact number of years. If you have details about Marc's astronaut career, please share them for a more accurate response.