Update AlertStatus record

I would like to update the an AlertStatus record programatically.

I am able to update the TriggerCount and the Notes field as well.  I would like to do an update of the LastUpdate record.

I am doing this is perl.

This is working:

       my $result = $swql->swis->Update($alert->{uri}, {

                                                    'TriggerCount'=> $alert->{triggercount} + 1,

                                                    'Notes' => $notes,

                                                   });

This is NOT working:

     my $time = '2014-04-17T17:31:18';

       my $result = $swql->swis->Update($alert->{uri}, {

                                                    'TriggerCount'=> $alert->{triggercount} + 1,

                                                     'LastUpdate'=> "CAST('".$time."' AS DATETIME)",

                                                    'Notes' => $notes,

                                                   });

Keep getting this error:

ERROR SolarWinds.InformationService.Core.InformationService - Exception caught in method Update

System.InvalidOperationException: Unable to cast from String to DateTime

   at SolarWinds.Data.Query.Expressions.ScalarExpression`1..ctor(T scalar, TypeInformation type)

   at SolarWinds.Data.Query.Expressions.QueryExpressionFactory.MakeScalarExpression[T](T value, TypeInformation type)

   at SolarWinds.InformationService.Core.CrudProcessor.MakeScalarExpression(Object value, TypeInformation typeInfo)

   at SolarWinds.InformationService.Core.CrudProcessor.MapPropertiesToColumns(IDictionary`2 properties, IMappingFragment fragment, IQueryExecutionContext context)

   at SolarWinds.InformationService.Core.CrudProcessor.UpdateInternal(Boolean bulkMode, SwisUriResolver uriResolver, IDictionary`2 propertiesToUpdate, IQueryExecutionContext context)

   at SolarWinds.InformationService.Core.CrudProcessor.Update(IServiceHost serviceHost, SwisUri uri, IDictionary`2 propertiesToUpdate, IQueryExecutionContext context)

   at SolarWinds.InformationService.Core.InformationService.Update(String uri, IDictionary`2 propertiesToUpdate)

',

    'faultMessage' => 'Unable to cast from String to DateTime',

    'faultstring' => 'Update failed, check fault information.'

Any assistance will be appreciated.

Charles