Using ARRAYJOIN in a regular formula


I have used ARRAYJOIN in rollups many times, but never tried it in a regular formula field, and I’m having some trouble.

I was trying to use ARRAYJOIN to create a string I can parse with DATETIME_PARSE. I’ll simplify the formula I wrote here to get rid of some complicating factors. The formula I tried was:


Airtable didn’t seem to understand square braces, curly braces or brackets, but I also couldn’t figure out any other wrapper for the array that would get it to work. All of the help articles I found are intended for rollups, where Airtable generates the array automatically. Anyone know how to do this? Thanks!