CPULoad query - SWQL Date Format

I have noticed one or two devices are always reporting an AvgLoad of 100%

I wrote this query to help us keep track, but are their any date functions available in SWQL?

     Ideally I want something along the lines:

          AND ObservationTimestamp > (UNIX_TIMESTAMP()-86400)

     or

          AND ObservationTimestamp > (NOW() - INTERVAL 1 DAY)

For now I have hardcoded a date:

SELECT NodeID, COUNT(*) as total

FROM Orion.CPULoad

WHERE ObservationTimestamp > '13/05/2014 00:00'

AND AvgLoad = 100

GROUP BY NodeID

    HAVING COUNT(*) > 4

ORDER BY COUNT(*) DESC;