9th November 2002 for me.
Bearing in mind that I live up in Edinburgh, it's a bit shit supporting a team in Scotland when you haven't been raised to support either side of the Old Firm. Plus, it's wrong, in my opinion to follow either Glasgow club when born in Edinburgh. My Dad took me to watch Hibs, but reality for me was, Scottish Football wasn't enjoyable.
My Dad, bless him, is a Rag fan. This come about my Great Grandad moved to Manchester for work and my Dad would go down with his Mum to visit him on the train. My Great Grandad took him to the swamp and that was it. He never forced the Rags on me as a kid though, but the 90's and Sky Sports in my house were infuriating as they won time and time again.
When the Goat bagged a brace on 9th November 2002 against them in the 3-1 win- I wound my old man up for days. Then I started cheering City when they were on the TV and in the years that followed, came down to watch them via train from Edinburgh Waverley to Manchester Piccadilly. I go at least 5 times a season...
Imagine his absolute fume when the takeover happened in 2008 and the pendulum swung in the blues favour - it's been the stuff of nightmares for him ever since....