You need to get an instance of the control on your page. Then you can call MasterViewDefinition.FilterExpression. This will get the filter that is set as a property of the control. Another option is overriding InitializeControls method MasterView that your widget uses and there check whether the dynamic filter expression returns results.
The third option is getting the date query from the url evaluator
var query = this.Manager.GetEvents();
query = this.EvaluateUrl(query, "Date", this.Host.DateEvaluatorPropertyName, this.Host.UrlEvaluationMode, this.Host.UrlKeyPrefix);
DataProviderBase.SetExpressions to see if there will be items returned by your control.
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