28   1. 

    28   1. Write the stub function, followed by the tests(demonstrating the

    29      failed tests), in turn followed by the code(demonstrating the

    30      passing tests) to calculate the number of days between two

    31      dates. Name your function num_of_days(). The function should take

    32      two arguments, both being tuples. Each tuple represents the date

    33      in the format of (dd, mm, yyyy) where dd, mm and yyyy are

    34      integers.

    35   2. Rewrite the num_of_days() function to take the start date as an

    36      optional argument. If the start date is not specified calculate

    37      the number of days between the only specified date since Unix

    38      epoch. Prior to manipulating the code to do this, make sure you

    39      change the tests, make them fail and then refactor the code.