diff --git a/fixedcal/core/date.py b/fixedcal/core/date.py
index b2b9553..a9437a2 100644
--- a/fixedcal/core/date.py
+++ b/fixedcal/core/date.py
@@ -1,37 +1,49 @@
 from datetime import datetime
 
 class FixedDate:
-    def __init__(self, date = None):
+    def __init__(self, date = None, day_of_year = None, year = None):
         if date is not None:
-            self._from_datetime(date)
+            init_tuple = self._from_datetime(date)
+        elif day_of_year is not None and year is not None:
+            init_tuple = self._from_day_of_year(day_of_year, year)
         else:
             raise ValueError("Invalid FixedDate initialization")
+        
+        self._day_of_year, self._year = init_tuple
 
-    def _from_datetime(self, _datetime):
-        day_of_year = _datetime.timetuple().tm_yday       # 1...
-        self._from_day_of_year(day_of_year, _datetime.year)
+    def _from_datetime(self, _datetime: datetime) -> tuple:
+        """Initialize this class with native datetime object.
 
-    def _from_day_of_year(self, day_of_year: int, year: int) -> None:
+        Args:
+            _datetime (datetime): _description_
+
+        Returns:
+            tuple: day of year (1...366) and year (1...9999) in a tuple
+        """
+        day_of_year = _datetime.timetuple().tm_yday
+        return self._from_day_of_year(day_of_year, _datetime.year)
+
+    def _from_day_of_year(self, day_of_year: int, year: int) -> tuple:
         """Initialize this class with day of year and year.
 
         Args:
             day_of_year (int): In range 1...366
             year (int): In range 1...9999
+
+        Returns:
+            tuple: day of year (1...366) and year (1...9999) in a tuple
         """
-        self._month, self._day_of_month = divmod(day_of_year-1, 28)
-        self._month += 1
-        self._day_of_month += 1
-        self._year = year
+        return (day_of_year, year)
 
     @property
     def day_of_month(self):
         """In range 1...29"""
-        return self._day_of_month
+        return ((self._day_of_year-1) % 28) + 1
 
     @property
     def month(self):
         """In range 1...13"""
-        return self._month
+        return ((self._day_of_year-1) // 28) + 1
 
     @property
     def year(self):
@@ -40,9 +52,12 @@ class FixedDate:
 
     @property
     def is_year_day(self) -> bool:
-        return self._month == 14 and self._day_of_month == 1
+        return self.month == 14 and self.day_of_month == 1
 
     # TODO: week of month
     # TODO: week of year
     # TODO: weekday
     # TODO: year quarter
+    # TODO: datetime instance
+    # TODO: plus and minus operations
+    # TODO: equatable
diff --git a/tests/date_test.py b/tests/basic_datetime_test.py
similarity index 95%
rename from tests/date_test.py
rename to tests/basic_datetime_test.py
index 03b1783..ca2d2c9 100644
--- a/tests/date_test.py
+++ b/tests/basic_datetime_test.py
@@ -2,10 +2,7 @@ import unittest
 from datetime import datetime
 from fixedcal.core.date import FixedDate
 
-class TestDate(unittest.TestCase):
-    def setUp(self):
-        pass
-
+class TestBasicDatetimeInit(unittest.TestCase):
     def test_datetime_init_january_first(self):
         fixed_date = FixedDate(date=datetime(2022, 1, 1))
         self.assertEqual(fixed_date.year, 2022)
diff --git a/tests/basic_day_of_year_test.py b/tests/basic_day_of_year_test.py
new file mode 100644
index 0000000..10e634f
--- /dev/null
+++ b/tests/basic_day_of_year_test.py
@@ -0,0 +1,36 @@
+import unittest
+from datetime import datetime
+from fixedcal.core.date import FixedDate
+
+class TestBasicDayOfYearInit(unittest.TestCase):
+    def test_day_of_year_init_january_first(self):
+        fixed_date = FixedDate(day_of_year=1, year=2022)
+        self.assertEqual(fixed_date.year, 2022)
+        self.assertEqual(fixed_date.month, 1)
+        self.assertEqual(fixed_date.day_of_month, 1)
+
+    def test_day_of_year_init_february_last(self):
+        fixed_date = FixedDate(day_of_year=56, year=2022)      # 2022-02-25 Gregorian
+        self.assertEqual(fixed_date.year, 2022)
+        self.assertEqual(fixed_date.month, 2)
+        self.assertEqual(fixed_date.day_of_month, 28)
+
+    def test_day_of_year_init_sol_month(self):
+        fixed_date = FixedDate(day_of_year=171, year=2022)      # 2022-06-20 Gregorian
+        self.assertEqual(fixed_date.year, 2022)
+        self.assertEqual(fixed_date.month, 7)
+        self.assertEqual(fixed_date.day_of_month, 3)
+
+    def test_day_of_year_init_december_last(self):
+        fixed_date = FixedDate(day_of_year=364, year=2022)      # 2022-12-30 Gregorian
+        self.assertEqual(fixed_date.year, 2022)
+        self.assertEqual(fixed_date.month, 13)
+        self.assertEqual(fixed_date.day_of_month, 28)
+        self.assertFalse(fixed_date.is_year_day)
+
+    def test_day_of_year_init_year_day(self):
+        fixed_date = FixedDate(day_of_year=365, year=2022)      # 2022-12-31 Gregorian
+        self.assertEqual(fixed_date.year, 2022)
+        self.assertEqual(fixed_date.month, 14)
+        self.assertEqual(fixed_date.day_of_month, 1)
+        self.assertTrue(fixed_date.is_year_day)