json schema date validation not suitable for mongodb - mongodb

Question

I'm using npm jsonschema module for nodejs and my very simple json schema looks like:
"title": "ticket",
"type": "object",
"properties": {
"_id" : {"type": "string"},
"created": {"type": "string", "format": "date-time"}
},
"additionalProperties" : false
The data I validate through this schema is stored in mongodb. The problem is that created property has an index with expireAfterSeconds to auto delete these records after certain amount of time.
Now I have the following problem. If I send a string (no matter if it's valid or invalid according to json specification), the document in the database also has created property with type string, as mongo db is schemaless and I can't predefine that property as date type. For example if I send the data with created property as 2017-08-15T14:34:18.839Z ISO string and although mongo date properties looks very similar they still remains string. Ofc this breaks the expires logic.
If I send my data with real date for created property, JSON validation fails with
instance.created is not of a type(s) string
Ofc I can transform all date fields on insert and update from validated string to date type but this is kinda not sufficient, because on read I will have data with real date types that will fail validation on next update. So I can include a back transformation on every read from date to string but still this solution is not good enough for me.
Any other ideas ?

Answer 1

Correct types for _id (which is ObjectID) and date types are:
"bsonType": "objectId" // for ObjectID
"bsonType": "date" // For ISODate
Example:
"title": "ticket",
"type": "object",
"properties": {
"_id" : {"bsonType": "objectId"},
"created": {"bsonType": "date"}
},
"additionalProperties" : false

Answer 2

Not familiar with jsonschema but if you were to use ajv you could make use of custom keywords and validation such as:
{
"type": "object",
"properties": {
"someDate": {
"instanceof": "Date"
}
}
}