You can tell because every shadow will show the weird shape of the sun. Here is a photograph of the shadows during an annular eclipse:

https://imgur.com/gallery/8c7rdEU

Whether or not people >1000 years ago would notice this and record it... I refrain from pretending to know.

It's not smart nor clever, but as a child I used to stare at the sun wide-eyed until my eyeballs teared up beyond my ability to keep them open any longer — easily thirty seconds and more.

My memory was of the sun itself distinctly resolving itself into a perfect circle with a sort of contrasting peripheral shadow that I recall describing as being 'like an aspirin pill'.

I blame some 80s TV show where an astronaut gained superhuman powers of some sort after staring directly at the sun.

I've always been curious to know what, if any, affect this has had on my vision (I don't have a terribly good capacity for resolving contrast during twilight).

In addition to the shadows, a cloud passing over in about a 2 hour window would make it apparent.