How to remove numeric validation for year in bib?

[cstby]

My understanding is that forthcoming is a perfectly valid value for the year field of a .bib citation. Right now, my build fails when entering forthcoming as a value. How can I remove this validation?

[george-gca]

Year is expected to be a number, so the publications are sorted and the most recent appears first. This is done in:

al-folio/_config.yml

Line 324 in 1bee4d1

group_by: year