Handling partial birthdays from vcf files

I have a bunch of contacts that I have birthdays stored for without their birth-year attached in my iCloud account. Apparently the way that Apple handles this is by exporting the VCF as the following:

BDAY;X-APPLE-OMIT-YEAR=1604:1604-05-09

This works fine in Apple's software, but not so much when attaching this to khal, as it will display their birth-year as 1604 (and thus, such contacts will be display as having their 413th birthday this year). I assume that Apple does this as a work-around to the official spec, and that there is no proper way to handle a date without a year attached to it. Since khal supports search a directory of .vcf files to get the birth date for each contact, is there a way to just have it display as "Jane Smith's Birthday" rather than "Jane Smith's 413th Birthday"?

Thanks.