Event dates defined in regular post and calendar

I publish prize games (sweepstakes if that is correct word) and I’d like to define begin date, end date and sweepstake date in regular post. I would define custom fields and I am interested is there a plugin that can use those fields and make a calendar.

I know there are calendar plugins but it seems most use custom post type. I would like to use regular post type. Any suggestin how to do it.

Tnx