A script that scrapes http://www.nationaldaycalendar.com/latest-posts/ and posts the "National day of" days to a slack channel.
Add a config.js file with the following vars:
slackChannel
slackToken
You can find those by going to this page:
https://api.slack.com/methods/channels.list/test
and testing the method with your team. You will get a url and a test response with a list of channels. There you can find the slack channel id. The url will contain the token.
I use a cronjob to run this every morning but I'm sure that's not the only method.