Cal.com
Open Source Meeting Scheduling Software
Meetings Pool Tool to find a time which works for everyone.
Samay is an open source tool to find a time which works for everyone. You can either host it yourself of use their free hosted service.
You can define slots in a calendar view and invite participants via a link to vote on the best time for a meeting or event. Samay automatically shows the participants the time in their local time zone and offers a simple interface to vote. You can either vote “Yes” or “If need be”.