I’ve had many checkpoints on my blog, and they all affected the visitor numbers, visitor activities and bounce rates differently.
To better understand the data, Google Analytics gives you the ability to add notes to your charts. This is very easy.
How do I do that?
Currently, you can not add notes in the Dashboard. You have to click on a subcategory of the data display to have this option.

If you do not see the arrow, your view is set to “Hourly”. The data display must be set to Daily.
As soon as the arrow is visible, click on it and then on “Create new note”. There you can pin your note to a specific day.

Conclusion
I have also learned this new feature and will use it first and see how powerful it is. I hope to learn what all the updates I’m programming for my blog affect it.