diff --git a/c3l_membership/utils.py b/c3l_membership/utils.py
new file mode 100644
--- /dev/null
+++ b/c3l_membership/utils.py
@@ -0,0 +1,15 @@
+from datetime import date
+
+
+def calculate_age(birthday):
+    today = date.today()
+    born = birthday
+    try:
+        birthday = born.replace(year=today.year)
+    except ValueError:
+        birthday = born.replace(year=today.year, month=born.month + 1, day=1)
+
+    age = today.year - born.year
+    if birthday > today:
+        age -= 1
+    return age