> c.find({a:{$gt:new Date()}} ).explain()
{
"cursor" : "BtreeCursor a_1",
"nscanned" : 0,
"nscannedObjects" : 0,
"n" : 0,
"millis" : 0,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" :

{ "a" : [ [ ISODate("2011-10-31T20:13:32.168Z"), ISODate("292278995-01--2147483647T07:12:56.808Z") ] ] }

}

> c.find({a:{$gt:new Date()}} ).explain().indexBounds.a[0][1].valueOf()
9223372036854776000

I think this value is generated by

void BSONObjBuilder::appendMaxForType( const StringData& fieldName , int t ) {
....
....
case Date:
appendDate( fieldName , numeric_limits<long long>::max() ); return;

Potentially this numeric value is invalid for a javascript date, but we might want to do something so the output looks a little nicer.

Also, there could potentially be other issues relating to date values outside an allowed js date range (round tripping, $where style queries, etc). So might be worth spending some time looking into these.