The end date for the PrimeGrid Birthday Challenge is stated wrongly.
It now shows as 2014-04-15 18:00 and the challenge is presented as 'completed'.
In reality the closing date is 2015-06-15 18:00:00(!) and the 3-day challenge has just started.

The problem is in their XML data:

<challenge>

    <id>68</id>

    <title><![CDATA[The PrimeGrid Birthday Challenge]]></title>

    <description><![CDATA[This is a 3 day Challenge on PrimeGrid's Sierpinski (SOB/PSP/ESP) Sieve application.]]></description>

    <startDate>Fri, 12 Jun 2015 18:00:00 UTC</startDate>

    <endDate>Mon, 15 Jum 2014 18:0:00 UTC</endDate>

    <link>http://www.primegrid.com/challenge/2015_challenge.php</link>

</challenge>

Reached out to PG, they will fix it. I updated the database manually.

Looks like the manual fix links to a moment in time, while the challenge -and the scores- go on.
My team is shown with 81,055 credits since the fix, but actually has scored 435,783.30 by now.
see PrimeGrid Birthday Challenge team scores here.

End date according to the Project challenges page is 2015-04-15 18:00 and therefore marked as completed. Should be 2015-06-15 18:00.

Unfortunately this was a PEBCAK error and computers only do as they are told.

So when PrimeGrid was notified of the faulty end date 2014-06-15 18:0:00 UTC,
they 'corrected' it to 2015-04-15 18:00 UTC? PEBCAK indeed -> replace user...