Add optional date parameter for weekend.

web_view.py

@@ -223,12 +223,19 @@ async def gaps_page() -> str:
 
 @app.route("/weekends")
 async def weekends() -> str:
-    """List of available gaps."""
-    today = date.today()
+    """List of available weekends using an optional date parameter."""
+    today = datetime.now().date()
+    date_str = flask.request.args.get("date")
+    if date_str:
+        try:
+            start = datetime.strptime(date_str, "%Y-%m-%d").date()
+        except ValueError:
+            return flask.abort(400, description="Invalid date format. Use YYYY-MM-DD.")
+    else:
+        start = date(today.year, 1, 1)
 
     current_week_number = today.isocalendar().week
 
-    start = date(today.year, 1, 1)
     trip_list = agenda.trip.build_trip_list()
     busy_events = agenda.busy.get_busy_events(start, app.config, trip_list)
     weekends = agenda.busy.weekends(start, busy_events)