diff --git a/lab25.py b/lab25.py
new file mode 100644
index 0000000..a81b5b1
--- /dev/null
+++ b/lab25.py
@@ -0,0 +1,35 @@
+def is_year_leap(year):
+    if year % 4 == 0:
+        return True
+    else:
+        return False
+
+def days_in_month(year, month):
+
+    days = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+
+    if is_year_leap(year) == True:
+        days[1] = 29
+
+    return days[month - 1]
+
+def day_of_year(year, month, day):
+    if month < 1 or month > 12:
+        return None
+    elif day < 1 or day > 31:
+        return None
+    elif day > 29 and is_year_leap(year) == True and month == 2:
+        return None
+    elif day > 28 and is_year_leap(year) == False and month == 2:
+        return None
+
+    day_ = day
+
+    for i in range(1,month):
+        mo = days_in_month(year,i)
+        day_ += mo
+
+    return day_
+
+print(day_of_year(2001,2,29)) 
+