Hi @Webcyberrob 
you were close. In FEEL, a date must be written within the date function: date("2020-01-01")
Since the FEEL date is not natively supported, you should set the input type to feel-date (or something else).
If you just need the year of the date then you can write it a bit shorter. See:
Does this help you?
Best regards,
Philipp