date_cal.py

# coding=utf-8
# Credit goes to Websten from forums  
#  
# Use Dave's suggestions to finish your daysBetweenDates  
# procedure. It will need to take into account leap years  
# in addition to the correct number of days in each month. 
#David Evans(University of Virginia)
  
def isLeapYear(year):  
    return (year % 4 == 0 and year % 100 != 0) or year % 400 == 0  
  
def daysInMonth(year, month):  
    if month in [1, 3, 5, 7, 8, 10, 12]:  
        return 31  
    elif month in [4, 6, 9, 11]:  
        return 30  
    else:  
        if isLeapYear(year):  
            return 29  
        else:  
            return 28  
  
def nextDay(year, month, day):  
    """Simple version: assume every month has 30 days"""  
    if day < daysInMonth(year, month):  
        return year, month, day + 1  
    else:  
        if month == 12:  
            return year + 1, 1, 1  
        else:  
            return year, month + 1, 1  
          
def dateIsBefore(year1, month1, day1, year2, month2, day2):  
    """Returns True if year1-month1-day1 is before year2-month2-day2. Otherwise, returns False."""  
    if year1 < year2:  
        return True  
    if year1 == year2:  
        if month1 < month2:  
            return True  
        if month1 == month2:  
            return day1 < day2  
    return False  
  
def daysBetweenDates(year1, month1, day1, year2, month2, day2):  
    """Returns the number of days between year1/month1/day1 
       and year2/month2/day2. Assumes inputs are valid dates 
       in Gregorian calendar."""  
    # program defensively! Add an assertion if the input is not valid!  
    assert not dateIsBefore(year2, month2, day2, year1, month1, day1)  
    days = 0  
    while dateIsBefore(year1, month1, day1, year2, month2, day2):  
        year1, month1, day1 = nextDay(year1, month1, day1)  
        days += 1  
    return days  


'''
def test():  
    test_cases = [((2012,1,1,2012,2,28), 58),   
                  ((2012,1,1,2012,3,1), 60),  
                  ((2011,6,30,2012,6,30), 366),  
                  ((2011,1,1,2012,8,8), 585 ),  
                  ((1900,1,1,1999,12,31), 36523)]  
      
    for (args, answer) in test_cases:  
        result = daysBetweenDates(*args)  
        if result != answer:  
            print "Test with data:", args, "failed"  
        else:  
            print "Test case passed!"  
  
test()  
'''