In my case, it was so long ago I honestly don't remember. It's certainly been for most of my adult life. I proudly bought the first issue of MS magazine, anyway. 
But I can tell you the moment my feminism was cemented for all time. I had just got off a bus after work, and was walking in front of two men who'd also got off at the same stop. One man was complaining to the other about working women taking jobs from men, and said, "They can always get a man to support them."
I so much wanted to tell him that I was 20-something years old, and hadn't had a man to support me since my father died when I was 10. I bit my tongue because I was tired and just wanted to get home - but I knew I had to speak up every chance I got after that.
(For the record, I am now 66 years old, and still have never had a man support me since my father died.)
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