By default an email sent the moment your subscriber reaches the "Send Message" step. What if they reach this step on a holiday (for example New Years), and you want it to wait until past the holiday?

All you have to do is add a "Wait" step beforehand. This is how you tell the automation step "Wait, before you proceed, make sure some conditions are met"

In the settings for the "Wait" step, you will want to enable time and day control, like so:

Then, you will want to choose your time window, and days of the week:

And then, select all the Holidays you want to exclude. Here's an example of excluding New Year's.