Question

I’m really confused and have been scratching my head over this for a few days now. I have a PHP script that stores some user profiles in a MongoDB. Users can login, change a few fields, and logout. When they login, it records the lastlogin date/time, and when you modify something it records the last modified date/time using the MongoDate object.

It works.. but sometimes.. and of course what appears randomly, the dates reset for specific documents to ‘ISODate("1969-12-31T16:00:00-08:00")‘

My documents store the dates like:

dates: {
    created: ISODate("1969-12-31T16:00:00-08:00"),
    lastlogin: ISODate("1969-12-31T16:00:00-08:00"),
    modified: ISODate("1969-12-31T16:00:00-08:00")
},

My PHP code looks like:

$collection->update(array('account.email' => $email), array('$set' => array('dates.lastlogin' => new MongoDate())));

Anyone have any ideas why?

Answer 1

MongoDate() represents a number of seconds since January 1st 1970 (ref: MongoDate::__construct).

The date you are seeing is the result of passing a value of an undefined variable or 0 (aka the unix epoch) to MongoDate().

Normally this value would be saved in MongoDB as:

 ISODate("1970-01-01T00:00:00Z")

However, because you have set your timezone to GMT -8 you are seeing the date offset by 8 hours, which becomes:

 ISODate("1969-12-31T16:00:00-08:00")