Using the Mongo shell:

Pre-SpiderMonkey (using an old nightly from 2009-05-04):

> db.test.remove()
> db.test.insert(

{'d':new Date(0)}

)

{"d" : "Thu Jan 01 1970 00:00:00 GMT+0000 (UTC)" , "_id" : "4a23b8615b7500843af9a5e3"}

With the latest nightly:

> db.test.remove()
> db.test.insert(

{'d':new Date(0)}

)
> db.test.find()
{"_id" : "4a23b88b02d692f259b63728" , "d" : {}}

Any idea why an empty object is inserted?