If you're using Support Professional or Enterprise, you can set a Schedule and mark Holidays easily as non-working days. Macro Date supports Holidays and multiple Schedules for Enterprise customers. This feature can be used to prevent Macro Date from selecting a relative working day that is actually a holiday. You can use the Schedules feature and Holidays just like you would normally do.
To make life more easy, you could consider to import Holidays using the pluscloud Holidays App on the Zendesk App Marketplace.
Set a Schedule for Macro Date
Due to limitations in Zendesk Support it's mandatory to actively set a Schedule in your Triggers. Normally, even with one Schedule Zendesk will automatically detect this Schedule. Zendesk is not capable to communicate the applied Schedule to integration such as Macro Date. For this reason, you should always add the following Trigger (or something a like) to your workflow:
Actions: Set Schedule > Name of your Schedule