diff --git a/.python-version b/.python-version
new file mode 100644
index 0000000..24ee5b1
--- /dev/null
+++ b/.python-version
@@ -0,0 +1 @@
+3.13
diff --git a/model/TimeSlot.py b/model/TimeSlot.py
index 9d2e458..cc00414 100644
--- a/model/TimeSlot.py
+++ b/model/TimeSlot.py
@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import datetime, timedelta
 
 
 class TimeSlot():
@@ -43,7 +43,7 @@ class TimeSlot():
     def end_now(self):
         self.end = datetime.now()
 
-    def duration(self) -> datetime.timedelta:
+    def duration(self) -> timedelta:
         end = self.end
         if not end: end = datetime.now()
         return end - self.start
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..10f950e
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,7 @@
+[project]
+name = "tt"
+version = "0.1.0"
+description = "Add your description here"
+readme = "README.md"
+requires-python = ">=3.13"
+dependencies = []
diff --git a/uv.lock b/uv.lock
new file mode 100644
index 0000000..547910c
--- /dev/null
+++ b/uv.lock
@@ -0,0 +1,8 @@
+version = 1
+revision = 3
+requires-python = ">=3.13"
+
+[[package]]
+name = "tt"
+version = "0.1.0"
+source = { virtual = "." }