Save time with the Schedule function for chat messages.
From any conversation, type in the message as usual, and click on 'Schedule'. You'll be asked to select a date and time in the future when you'd like to have the message sent automatically.
All the scheduled messages will appear in the chat conversation below the hour when they were scheduled. Once they are sent, the message will be displayed under the hour when it was sent.
You can also see at a glance if any messages are scheduled by checking the bubble next to the 'Schedule' button. Clicking on it will display all the messages about to be sent. From there, you can also delete any message that's no longer relevant.