I can't remember the URL for the life of me, but there was a website that was doing this, at the international level, for multiple democracies. Last I remember, the site stopped updating - it was a volunteer led effort.

It would be awesome to have a single place that has both history and the upcoming elections. Ideally, this should be done by the government, as they are in the best position to do so. Second best would be some kind of volunteer led effort. It is a ton of work though, to keep the information accurate and current