In Mail.app, when the text looks like an appointment (date and time, etc) you are offered a shortcut to add it as an event in the Calendar app. There is no such thing in Safari (as far as I can tell.) Has anyone done an add-in or other trick to accomplish that?
If you have a force touch trackpad (built in or magic trackpad) you can force touch on dates, and then you'll be able to add them to your calendar.
If you don't have a force touch trackpad, but a normal trackpad, you can just move the cursor on top of a date, and the touch the trackpad with three fingers, and then you'll be able to add them to your calendar.