How to Add a Reminder in Slack

Step 1: To see how the command needs to be set up, log in to Slack and, in the comment field,
type /remind. A pop-up will show you how to structure the command.

Step 2: Always precede the name of the person with the @ symbol or the name of the channel with the # symbol.
If you’re reminding yourself, just use me without the @ symbol. Follow the /remind command with the person
you want to set the reminder for, the reminder, and the date for the reminder.

Step 3: When you press Enter, you’ll see a message confirming that Slack will remind you at the date and time you specified.
You’ll also see buttons to Delete the reminder or View Reminders that you’ve already set.

Step 4: Reminders appear in the Slackbot channel. You’ll see a notification icon appear there when the reminder is active.
If you select the channel, you’ll see the most recent reminders. You can select Mark as Complete, Delete to remove the reminder, or Snooze the reminder to receive the reminder notification again later.

Credit : https://www.lifewire.com/using-slack-reminders-4843714