API using date range (no replies)

Hi all

I'm using http://analytics.example.org/index.php?module=API&method=Actions.getPageUrls&idSite=9&period=range&date=2013-07-22,2013-07-28&format=csv&filter_limit=5000&flat=1 with my token at the end & obviously pointing to my real Piwik server.

But it gives me this error :

'Error: The date '2013-07-22' is not a correct date range. It should have the following format: 'lastN', 'previousN', 'YYYY-MM-DD,YYYY-MM-DD'.'

If I use exactly the same string but change period to MONTH or DAY the report pulls correctly!

Why doesn't a date range work on the API?

thanks
Lynn