JSON Date format (without time) returning from an API

Wondering if I should remove the time data normally stored. We're using postgres and node.js where a DateTime would get returned from our API as:

2013-07-01T00:00:00.000Z

Yet since this field should only represent a date, I feel reformatting before return like this would make it more clear that time is not relevant:

2013-07-01

Thoughts?

As an API user, I would much rather receive the long form of a date.

For a few reasons:

  1. Time Zone: the long format actually has a time-zone built in. That's important.
  2. Parsing: most languages will be able to read that long format as a native "Date" object. In some languages like C# & Java, that short date will need to be coerced into using the correct time zone. You also avoid Month/Day confusion with the long format.
  3. Comparisons: if a user passes in a short date, is your API going to handle that correctly? A good API needs to look the same going in and out.