When keeping cancellation date as blank:
click on Save and Continue button throwing server error.
Form partner and employee login
Refer attached screen shots and below error log:

Exception : String was not recognized as a valid DateTime.
App Error Log : -
Employee ID : 4709
Action Name : AddUpdateCoordinationOfBenefits
Model : System.Web.Mvc.HandleErrorInfo
Controller : UserDetails
Web Error Log : at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
at WORKTERRA.BenAdmin.Areas.UserDetails.Models.CoordinationOfBenefitsModel.GetCOBForSave(CoordinationOfBenefitsModel objCoordinationOfBenefits)
at WORKTERRA.BenAdmin.Areas.UserDetails.Models.CoordinationOfBenefitsModel.AddUpdateCoordinationofBenefits(CoordinationOfBenefitsModel objCoordinationOfBenefits, Int64 ID)
at WORKTERRA.BenAdmin.Areas.UserDetails.Controllers.UserDetailsController.AddUpdateCoordinationOfBenefits(CoordinationOfBenefitsModel objCoordinationOfBenefits)
at lambda_method(Closure , ControllerBase , Object[] )
at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.b__3d()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c_DisplayClass46.b_3f()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c_DisplayClass46.b_3f()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c_DisplayClass33.b_32(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c_DisplayClass21.<>cDisplayClass2b.b_1c()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c_DisplayClass21.b_1e(IAsyncResult asyncResult)