Create an ISO date object in javascript
Try using the ISO string
var isodate = new Date().toISOString()
See also: method definition at MDN.
try below:
var temp_datetime_obj = new Date();
collection.find({
start_date:{
$gte: new Date(temp_datetime_obj.toISOString())
}
}).toArray(function(err, items) {
/* you can console.log here */
});