Alternate option using random.org

[mathiasbynens]

Apparently random.org supports creating a fixed random number for a certain date, via a URL that can be shared & verified, e.g.:

https://www.random.org/integers/?num=1&col=1&base=10&min=1&max=50&format=html&rnd=date.2022-07-09

For any dates in the future, it errors:

Error: No randomization exists for that date

So that's another approach that could work.