Slack: Schedule Messages
When you have an important message to share in Slack, but it's not the best time to send it quite yet, you can schedule it. Select a date and time in the future and rest assured your message will be sent whether you're at your desk or on the go.
 Instructions
Click the compose button or open the conversation where you'd like to send your message.
Type your message in the message field.
Click the arrow icon to the right of the paper plane icon.
Choose a date and time from the list or select Custom time.
Note: Scheduled messages cannot be posted as a reply to a thread.
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