How to reproduce

• Access piwik with a date range (demo.piwik.org)
• Access Email reports
• Download any report

Error is :

<result>
<error message="Date format must be: YYYY-MM-DD, or 'today' or 'yesterday' or any keyword supported by the strtotime function (see http://php.net/strtotime for more information)"/>
</result>

The API call to PDFReports.generateReport is set with

period=range&date=datex,datey

period is overridden with configured period report in
/plugins/PDFReports/API.php#L243

getProcessedReport is called with

period=month or week or day&date=datex,datey

/plugins/API/API.php#L360 is executed and throws an exception at /core/Date.php#L70 because the Date factory doesn't support date ranges.

Solutions

• Override date with only one of the two provided dates
• Allow date range scoped pdf reports when manually downloaded ?
• Anything else ?