Schedule a message in Slack

I need to send a message in slack at a time set in advance.

Is there a way to do it through the Slack API or do I need to have a script running and checking if it's time to send the message and then send it?

You should be able to create a reminder sending a message to @slackbot The message should be like:

/remind [@someone or #channel] [what] [when]

Here's some examples:

/remind @username to do something in 24 hours

or:

/remind @username to do something at 16:00

You can use this free Slack application to send scheduled and self-destruct messages. https://timy.website

1. Sending a scheduled message

/send Happy birthday at 12am

/send Happy birthday in 1h30m

2. Sending a self-destruct message

/delete Secret message! at 2pm

/delete Secret message! in 3h

You can find more details on the website.