This bot lets you post events (tasks or room bookings) from an online calendar into a telegram chat group, so people can sign up for them. It's designed to help (public/collective/participatory/collaborative) groups to organize work.

after you created an event or a task in your calendar

post it in your telegram group/channel, so a person can assign hirself

This software is open source. You are in control, because each group has its own Bot. And it can be used free of charge via heroku.

Depending on the calendar you want to use, following telegram bots are available:

• you already using an online calendar, like the google calendar, nextcloud, owncloud etc.? Then try the CalDAV-telegram-bot
• if you don't have a calendar yet and you prefer a simple 1-click solution, check out the teamup calendar and the teamup-telegram-bot