This is doable, though there’s no way to sort the dates because Airtable does not have any sorting options in its formula structure. If sorted dates are important, you’ll need to skip the description below and do everything in a script (either in the Scripting app, or in an automation). If you’d like help with that setup, let us know.
Here’s the end result of the formula version:
To set this up, you’ll first need to add a formula field named {Year}
to your [Dates]
table, using this formula (replace “Date” with the reference to your date field):
YEAR(Date)
In your main table, add a rollup field named {Year Rollup}
to roll up the values from this new {Year}
field based on the links in the {Dates (if known)}
field. The aggregation formula should be:
ARRAYJOIN(values, ", ")
This will create a string containing comma-separated years based on the linked dates.
The formula for the {Year Overlay}
field would then be this:
IF({Year Rollup}, {Year Rollup} & IF({Year (if date not known)}, ", ")) & IF({Year (if date not known)}, {Year (if date not known)})