目前有个查询条件需要两个日期相减大于多少小时为条件，囧不知道怎么写，求大神们指教！！

顶一个。

db.new_receive_detail.aggregate([
{$match:{
receiveStatus:"qced",
receiveOn :{
$gt: ISODate("2017-12-20T23:59:59.928Z")
}
// billNo:"CE201712210086"
}
},
{
$project: {
skuReceiveType:"$skuReceiveType",
receiveQty : "$receiveQty",
times: { $subtract:["$surfaceOn","$receiveOn" ]},
skuAvgTime:{$divide: ["$times", "$receiveQty"]}
}
},
{
$project: {
skuReceiveType:"$skuReceiveType",
receiveQty : "$receiveQty",
times: "$times",
skuAvgTime:{$divide: ["$times", "$receiveQty"]}
}
},
{
$match:{
times:{
$gt: 0
}
}
},
{
$group: {
_id:{
skuReceiveType:"$skuReceiveType"
},
avgTime : {
$avg: "$skuAvgTime"
}
}
},
{
$project: {
times33: { $divide:["$avgTime",1000 ]}
}
}
]);

这个$subtract:["$surfaceOn","$receiveOn" ] 函数 就是时间先减