You can set reminders for yourself on specific tasks.

To set a reminder, go to the desired task, click on the "more icon" at the top right of the task window, then choose Change task > Set reminder

You can also hit the "H" button on your keyboard as a shortcut to reveal a popup with a variety of reminder options, as well as the option to enter your own desired date or time:

When a reminder is triggered, it will remind you at the desired day or time.

In Dart, when a reminder is triggered, you will see a countdown to the reminder beside the title:

Once the reminder deadline is hit, a purple dot will appear by that task:

If you have your notifications settings activated, you will also get an email. Email reminders are set by default in Dart, however, this can be adjusted in your notification settings.

You can change your notification settings, and decide how you will get notified (via email, in-app) by going to:

Settings > Notifications > Reminders