User input Date validation error is logged into ERROR log

Error log contains some ERROR messages which seems as caused by "normal" user validation and shouldn't be in error log.

2010-09-19 13:09:53,758 ERROR [btpool0-4376] fisheye.app com.cenqua.fisheye.web.WaybackSpecChart$Params-getObject - Error parsing date string arigons3456@gmail.com
java.text.ParseException: Unparseable date: "arigons3456@gmail.com"
at java.text.DateFormat.parse(DateFormat.java:337)
at com.cenqua.fisheye.web.WaybackSpecChart$Params.getObject(WaybackSpecChart.java:467)
at com.cenqua.fisheye.web.WaybackSpecChart.fromRequest(WaybackSpecChart.java:160)
at com.cenqua.fisheye.web.WaybackSpecChart.fromRequest(WaybackSpecChart.java:138)
at com.cenqua.fisheye.web.ChartPageAction.handleWaybackJump(ChartPageAction.java:40)
at com.cenqua.fisheye.web.ChartPageAction.handleRequest(ChartPageAction.java:56)
at com.cenqua.fisheye.web.BaseAction.processRequest(BaseAction.java:181)
at com.cenqua.fisheye.web.ActionDispatcherServlet.doIt(ActionDispatcherServlet.java:224)
at com.cenqua.fisheye.web.ActionDispatcherServlet.doGet(ActionDispatcherServlet.java:55)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:502)