From 14f5baf77cc662349f9dbed999549a6eb19dc90e Mon Sep 17 00:00:00 2001
From: Edward Betts <edward@4angle.com>
Date: Mon, 22 Jun 2026 09:08:33 +0100
Subject: [PATCH] Validate conference date ranges

---
 validate_yaml.py | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/validate_yaml.py b/validate_yaml.py
index 1e5b29e..c8d4022 100755
--- a/validate_yaml.py
+++ b/validate_yaml.py
@@ -17,6 +17,7 @@ import agenda.data
 import agenda.travel
 import agenda.trip
 import agenda.types
+import agenda.utils
 
 config = __import__("config.default", fromlist=[""])
 data_dir = config.PERSONAL_DATA
@@ -267,6 +268,23 @@ def check_trains() -> None:
     print(len(trains), "trains")
 
 
+def check_conference_dates(conf: agenda.conference.Conference) -> None:
+    """Check conference start/end range."""
+    if normalize_datetime(conf.start) > normalize_datetime(conf.end):
+        pprint(conf)
+        print(f"conference {conf.name!r} ends before it starts")
+        sys.exit(-1)
+
+    duration = (agenda.utils.as_date(conf.end) - agenda.utils.as_date(conf.start)).days
+    if duration >= agenda.conference.MAX_CONF_DAYS:
+        pprint(conf)
+        print(
+            f"conference {conf.name!r} is {duration} days; "
+            + f"maximum is {agenda.conference.MAX_CONF_DAYS - 1}"
+        )
+        sys.exit(-1)
+
+
 def check_conferences() -> None:
     """Check conferences and ensure they are in chronological order."""
     filepath = os.path.join(data_dir, "conferences.yaml")
@@ -285,6 +303,7 @@ def check_conferences() -> None:
             sys.exit(-1)
 
         check_country_code(conf_data, "conference", required=False)
+        check_conference_dates(conf)
 
         current_start = normalize_datetime(conf_data["start"])
         if prev_start and current_start < prev_start: