What is the best gem for managing con jobs?

I want to write a cron job in order to shoot a notification about an event happening soon. I want to notify the participants about the event one day before it's happening day. I want to call a controller method which will check event start date and if it is happening tomorrow it should be called automatically and send notifications to the participants.I tried whenever gem but did not work for me or might be I don't know how to use it for my case. Please suggest me a good gem which will fit in my use case. Thanks.