[Developers] Having trouble with a query

[Norbauer Alan]

I'm having trouble getting a query to work.  I'm trying to search on  
the "Open Times" of retail locations without much luck.  Despite the  
documentation saying that this is a "Date/Time", it doesn't appear to  
behave as such.  For example, the following works:

{
   "query":[{
     "/business/retail_location/hours":[{
       "hour_end":{
         "value":null
       },
       "weekday_start":"Saturday"
     }],
     "limit":4,
     "name":null,
     "sort":"name"
   }]
}

Meanwhile, the following doesn't:

{
   "query":[{
     "/business/retail_location/hours":[{
       "hour_end":{
         "value>=":"15:00"
       },
       "weekday_start":"Saturday"
     }],
     "limit":4,
     "name":null,
     "sort":"name"
   }]
}

And neither does:

{
   "query":[{
     "/business/retail_location/hours":[{
       "hour_end>=":"15:00",
       "weekday_start":"Saturday"
     }],
     "limit":4,
     "name":null,
     "sort":"name"
   }]
}

I'm trying to make heads or tails of all these braces and brackets  
and it's driving me nuts.

Any help here?

Relevant docs:
Retail Location type: http://www.freebase.com/view/schema?id=% 
2Fbusiness%2Fretail_location
Open Times type: http://www.freebase.com/view/schema?id=%2Fbusiness% 
2Fopen_times
Date/Time type: http://www.freebase.com/view/schema?id=%2Ftype% 
2Fdatetime

^^^^ The Date/Time documentation is quite perplexing... it appears to  
have nothing to do with a date or time?

Thanks in advance,
Alan