1976 with Chainmail and some D&D then moved to AD&D in 77. My younger brother and his group needed a DM and got hooked.
You’re definitely not an imposter. Doesn’t matter where, when, how you started. Just enjoy.Reading the other replies, I feel like the imposter.
First time I played D&D was probably in 2001 or 2002. Played one session of 2nd edition with a teacher. I didn't understand much. And a few weeks later a friend got the 3rd edition Player's Handbook and we started short 3rd edition campaign with that teacher.