This tool makes it really easy to edit/add datetimes in Holidays.dbc. I know it works for 3.3.5, unsure about other versions. some of the dates use the year, some don't. Some use the day of week, some don't.
Example of it working with Sept 19th (Pirate day)
[attachment=1:1vxh8tin]proofifproofwere needed.png[/attachment:1vxh8tin]
