Changes

You must name your python 3 script as <code>a1_[Student_id].py</code>. The following examples assumes that the student_id is rchan.The script should accept two command line arguments, the first one is the date in "YYYY/-MM/-DD" format, and the second one is the number of day from the given date, a positive value indicates the number of days after the given date, and a negative value indicates the number of days before the given date. There is an optional flag called --step which can be provided at the command line that makes the program print out all dates until the target date. If the "YYYY-MM-DD" format is broken, your script should give an appropriate error message. Invalid months (>12) or invalid days of month(different for each month), should be detected and give appropriate error messages. For examples: