&date=last10 does not work in the iframe of dashboard widget

H i there, I try to embed my piwik dashboard in my website by using iframe, I wanna it display last 10 days data by default, so my iframe is:

<iframe src="http://www.piwiktest.com/index.php?module=Widgetize&action=iframe&moduleToWidgetize=Dashboard&actionToWidgetize=index&idSite=1&period=day&date=last10"></iframe>

but I found the “&date=last10” parameter does not work. if I use this code in my iframe src, it will show a error “Date format must be: YYYY-MM-DD, or ‘today’ or ‘yesterday’ or any keyword supported by the strtotime function (see PHP: strtotime - Manual for more information):” , so is there a solution for this issue? thanks!