500 Servlet Exception

java.lang.Exception: java.text.ParseException: Unparseable date: ""
	at au.util.DateTools.stringToDate(DateTools.java:210)
	at _www._traffic._flight_0search__jsp._jspService(/home/www/www/traffic/flight_search.jsp:233)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:75)
	at com.caucho.jsp.Page.subservice(Page.java:506)
	at com.caucho.server.http.FilterChainPage.doFilter(FilterChainPage.java:182)
	at com.caucho.server.http.Invocation.service(Invocation.java:315)
	at com.caucho.server.http.CacheInvocation.service(CacheInvocation.java:135)
	at com.caucho.server.http.RunnerRequest.handleRequest(RunnerRequest.java:346)
	at com.caucho.server.http.RunnerRequest.handleConnection(RunnerRequest.java:274)
	at com.caucho.server.TcpConnection.run(TcpConnection.java:139)
	at java.lang.Thread.run(Thread.java:619)
Caused by: java.text.ParseException: Unparseable date: ""
	at java.text.DateFormat.parse(DateFormat.java:337)
	at au.util.DateTools.stringToDate(DateTools.java:204)
	... 10 more