first day and end day on month

gistfile1.txt

def firstOfMonth(day):
    resultDate = day.replace(day=1)

    if ((day - resultDate).days > 25):
        resultDate = resultDate + relativedelta(months=1)

    return resultDate

def lastOfMonth(any_day):
    next_month = any_day.replace(day=28) + datetime.timedelta(days=4)  # this will never fail
    return next_month - datetime.timedelta(days=next_month.day)


def monthdelta(date, delta):
    m, y = (date.month+delta) % 12, date.year + ((date.month)+delta-1) // 12
    if not m: m = 12
    d = min(date.day, [31,
        29 if y%4==0 and not y%400==0 else 28,31,30,31,30,31,31,30,31,30,31][m-1])
    return date.replace(day=d,month=m, year=y)


print(firstOfMonth(datetime.date.today()))
print lastOfMonth(datetime.date(2017, 8, 11))
print(monthdelta(datetime.date.today(), -1))