I didn't know about "an historic" until I heard it from American journalists. They did pronounce the 'h' and it did indeed sound very wrong. I believe I first heard it from Rachel Maddow. I can't find any clips, but there are a bunch of transcripts from her show if you search up:
reply> Rachel Maddow "an historic day"
For example:
It's one of those things American pseudo intellectuals do because they think it's more correct and want to sound superior. Maybe they heard a professor say it that way or read it in a book. Anything but actually process why the a/an distinction exists.
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