How do you create a calendar event link to add in an email?

How do you create an “Add to Calendar” links for emails?
example: Add to Calendar: Outlook® Calendar | Google Calendar™ | iCal®

NovakSolutions gives you a tool for that, it’s called the Email Appointment Tool.
You can find info on it here:
Tools — Novak Solutions (you’ll see it on the fourth row from the top)