Suppose you are building an API, and you receive a JSON. You want to parse & save that JSON to the
DB - but your dates are strings (the JSON way). So what you do is store the datifyed version. You might:

collection.insert(datify(JSON.parse(payload)),function(){/* do something*/});

Suppose you are using an API (from the browser, for example), that have dates in it, as strings (it is JSON, after all) - you just datify it.