The qRules SubmitToSharePointList command is a great way to get information from your InfoPath form into a SharePoint List - however, there was recently a thread in the forum where a qRules user was having problems submitting form data to a Calendar. The error was:
"Errors occurred submitting to list: Invalid date/time value. A date/time field contains invalid data. Please check the value and try again."

Turns out the date time for the Calendar list required a different format:
yyyy-MM-ddTHH:mm:ssZ

The qRules format data command can return a date with a custom format - so, if you need to submit to a calendar, you may want to leave regular date time controls on your form for your users to select with, but have another field that is mapped to your SharePoint list. Set that field to the result of the FormatDate command, so that your Start and End date have the correct format prior to submitting.