beginning of leap support

fixedcal/core/date.py

@@ -1,5 +1,5 @@
 from datetime import datetime, timedelta
-from math import floor
+from fixedcal.services.leap_days import is_leap_year, gregorian_leap_days_between, fixed_leap_days_between
 
 class FixedDate:
     def __init__(self, date = None, day_of_year = None, year = None):
@@ -40,6 +40,18 @@ class FixedDate:
     def today(self) -> "FixedDate":
         return FixedDate(date=datetime.today())
 
+    @property
+    def is_leap_year(self) -> bool:
+        """Whether the year of this date is leap year.
+
+        Returns:
+            bool: Is this leap year
+        """
+        # if self._year % 100 == 0:
+        #     return self._year % 4 == 0 and self._year % 400 == 0
+        # return self._year % 4 == 0
+        return is_leap_year(self._year)
+
     @property
     def datetime(self) -> datetime:
         """Construct a native datetime object from fixed date.
@@ -149,7 +161,10 @@ class FixedDate:
             With timedelta as argument, new FixedDate will be returned.
         """
         if isinstance(o, FixedDate):
-            return self.datetime - o.datetime
+            difference = self.datetime - o.datetime
+            greg_leap_days = gregorian_leap_days_between(self.datetime, o.datetime)
+            fixed_leap_days = fixed_leap_days_between(self.datetime, o.datetime)
+            return difference - timedelta(greg_leap_days) + timedelta(fixed_leap_days)
         elif isinstance(o, timedelta):
             new_date = self.datetime - o
             return FixedDate(date=new_date)

fixedcal/services/leap_days.py

@@ -0,0 +1,38 @@
+from datetime import datetime, timedelta
+
+def is_leap_year(year: int) -> bool:
+    if year % 100 == 0:
+        return year % 4 == 0 and year % 400 == 0
+    return year % 4 == 0
+
+def gregorian_leap_days_between(date1: datetime, date2: datetime) -> int:
+    """Counts the gregorian leap days (29th Feb) between given dates.
+    Count includes both ends (date1 and date2 themselves).
+
+    Args:
+        date1 (datetime): The beginning of the count
+        date2 (datetime): The end of the count
+
+    Returns:
+        int: Count of the leap days.
+    """
+    count = 0
+    if date1 > date2:
+        date1, date2 = date2, date1
+    days_between = (date2 - date1).days
+    for plusday in range(0, days_between):
+        date = date1 + timedelta(plusday)
+        if is_leap_year(date.year) and date.month == 2 and date.day == 29:
+            count += 1
+    return count
+
+def fixed_leap_days_between(date1: datetime, date2: datetime) -> int:
+    count = 0
+    if date1 > date2:
+        date1, date2 = date2, date1
+    days_between = (date2 - date1).days
+    for plusday in range(0, days_between):
+        date = date1 + timedelta(plusday)
+        if is_leap_year(date.year) and date.month == 6 and date.day == 27:
+            count += 1
+    return count

tests/leap_year_test.py

@@ -0,0 +1,61 @@
+import unittest
+from datetime import datetime, timedelta
+from fixedcal import FixedDate
+
+class TestLeapYear(unittest.TestCase):
+    def test_leap_year_detection_with_simple_noleap(self):
+        # 2022 is not divisible of four -> not a leap year
+        fixed_date = FixedDate(datetime(2022, 5, 4))
+        self.assertFalse(fixed_date.is_leap_year)
+
+    def test_leap_year_detection_with_complex_noleap(self):
+        # 1900 is divisible of four but also by 100 and not by 400 -> not a leap year
+        fixed_date = FixedDate(datetime(1900, 5, 4))
+        self.assertFalse(fixed_date.is_leap_year)
+
+    def test_leap_year_detection_with_common_leap_year(self):
+        # 2024 is divisible of four but not by 100 -> leap year
+        fixed_date = FixedDate(datetime(2024, 5, 4))
+        self.assertTrue(fixed_date.is_leap_year)
+
+    def test_leap_year_detection_with_centurial_leap_year(self):
+        # 2000 is divisible of all four, 100 and 400 -> leap year
+        fixed_date = FixedDate(datetime(2000, 5, 4))
+        self.assertTrue(fixed_date.is_leap_year)
+
+    def test_fixed_date_difference_over_gregorian_leap_day(self):
+        # in Gregorian system there are 7 days between,
+        # but in IFC the leap day is at the end of June
+        # and thus the difference should be just 6 days
+        date1 = FixedDate(datetime(2024, 2, 25))
+        date2 = FixedDate(datetime(2024, 3, 3))
+        self.assertEqual(date2-date1, timedelta(6))
+
+    def test_fixed_date_difference_over_fixed_leap_day(self):
+        # in Gregorian system there are 7 days between,
+        # but in IFC the leap day is also in between
+        # and therefore the difference should be 8 days
+        date1 = FixedDate(datetime(2024, 6, 27))
+        date2 = FixedDate(datetime(2024, 7, 4))
+        self.assertEqual(date2-date1, timedelta(8))
+
+    def test_fixed_date_difference_with_itself_gregorian_leap_day(self):
+        date = FixedDate(datetime(2024, 2, 29))
+        self.assertEqual(date-date, timedelta(0))
+
+    def test_fixed_date_difference_with_itself_fixed_leap_day(self):
+        date = FixedDate(datetime(2024, 6, 27))
+        self.assertEqual(date-date, timedelta(0))
+
+    def test_fixed_date_difference_over_both_leap_days(self):
+        # day count should be the same in both systems
+        date1 = FixedDate(datetime(2024, 2, 15))
+        date2 = FixedDate(datetime(2024, 8, 3))
+        self.assertEqual(date2-date1, timedelta(170))
+
+    def test_fixed_date_difference_over_multiple_leap_days(self):
+        # there are 3 Gregorian and 2 fixed leap days between
+        # difference is 2987 days in Gregorian including Greg leap days
+        date1 = FixedDate(datetime(2020, 2, 15))
+        date2 = FixedDate(datetime(2028, 4, 20))
+        self.assertEqual(date2-date1, timedelta(2986))