Sharepoint 2013 workflow internal status goes to Canceled with a System.FormatException

I am running a workflow attached with task pages. The workflow has been designed in visual studio 2012. After completing the first task page, the internal status of the workflow will change to Canceled. the below is the error I am getting. Please help me out with this.

RequestorId: 6fc2171f-7658-3d35-ff1a-a3e003c4f5f4. Details: System.FormatException: String was not recognized as a valid DateTime. at System.DateTime.Parse(String s, IFormatProvider provider) at System.Activities.CodeActivity`1.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager) at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation)