In your menu go to "Marketing" and click "CTAs"

You can then choose to use a pre-built CTA

Or you can click on "Blank" to create from scratch

Once you click on "Black", choose the option you want and click "Choose template"

You will now see the option for the Countdown Timer which to can pick up and drag into your template

The click on the module to edit the timer date and display options

Remember to click on "Targeting" to setup the pages you want the CTA to appear on

And scroll down you'll see that HubSpot has already set the CTA to unpublish after the event date.

When you're done click "Review and publish"

HubSpot is a CRM platform. Learn how to effectively use HubSpot to manage your customers and other tips and tricks such as how to merge contacts or how to connect your Gmail account.