MongoDB: Fix string-typed MongoDate fields
db.jobseekers
// Find all documents with a string-typed date field
.find({date: {$type: 2}})
// Convert each date field to a ISODate based on its "created_on" raw timestamp
.forEach(function(doc) {
// The JSON <date> representation that Mongo expects is a 64-bit signed
// integer representing milliseconds since the epoch.
// We need to multiply the unixtime seconds value by 1000.
//
// @see: http://docs.mongodb.org/manual/core/import-export/#data-type-fidelity
doc.date = new Date(doc.created_on * 1000);
// Save modified doc
db.jobseekers.save(doc);
});