etdays
==============================================

Purpose
----------------

Computes the difference between two times, as generated by the :func:`date` command, in days.

Format
----------------
.. function:: days = etdays(t_start, t_end)

    :param t_start: starting date, in the order:
        yr, mo, day. (Only the first 3 elements are used.)
    :type t_start: 3x1 or 4x1 vector

    :param t_end: ending date, in the order:
        yr, mo, day. (Only the first 3 elements are used.)
        MUST be later than *tstart*.
    :type t_end: 3x1 or 4x1 vector

    :return days: elapsed time measured in days.

    :rtype days: scalar

Examples
----------------

::

    // Set start date
    t_start = { 2008, 1, 2 };

    // Set ending date
    t_end = { 2009, 9, 14 };

    // Calculate elapsed number of days
    d = etdays(t_start, t_end);

After the code above, *d* is equal to:

::

    621

Remarks
-------

This will work correctly across leap years and centuries. The
assumptions are a Gregorian calendar with leap years on the years evenly
divisible by 4 and not evenly divisible by 100, unless divisible by 400.


Source
------

time.src

.. seealso:: Functions :func:`dayinyr`