From df278007bf4d354b89af0074deb33454b655437a Mon Sep 17 00:00:00 2001
From: jessikitty <jess.rogerson.29@outlook.com>
Date: Sun, 23 Aug 2026 00:05:11 +1000
Subject: [PATCH] Add time-zone-aware Clock helper for Meow expiry checks

---
 Infrastructure/Clock.cs | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 Infrastructure/Clock.cs

diff --git a/Infrastructure/Clock.cs b/Infrastructure/Clock.cs
new file mode 100644
index 0000000..5c21d66
--- /dev/null
+++ b/Infrastructure/Clock.cs
@@ -0,0 +1,40 @@
+namespace NoticeBoard.Infrastructure;
+
+/// <summary>
+/// Single source of "now" for Meow expiry checks, so the picker (browser wall-clock,
+/// no time zone info) and the server's comparison always agree on what "now" means.
+///
+/// Configured once at startup from the "TimeZone" setting (an IANA id like
+/// "Australia/Melbourne", or "UTC"). Leaving it blank falls back to the host
+/// machine's own local time zone — the original IIS behaviour, unchanged.
+/// </summary>
+public static class Clock
+{
+    private static TimeZoneInfo _timeZone = TimeZoneInfo.Local;
+
+    public static void Configure(string? timeZoneId)
+    {
+        if (string.IsNullOrWhiteSpace(timeZoneId))
+        {
+            _timeZone = TimeZoneInfo.Local;
+            return;
+        }
+
+        try
+        {
+            _timeZone = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId);
+        }
+        catch (TimeZoneNotFoundException)
+        {
+            // Unknown id (e.g. tzdata missing, or a typo) — UTC is a safe, unambiguous fallback.
+            _timeZone = TimeZoneInfo.Utc;
+        }
+        catch (InvalidTimeZoneException)
+        {
+            _timeZone = TimeZoneInfo.Utc;
+        }
+    }
+
+    /// <summary>Current time in the configured server time zone — directly comparable to a stored ExpiresAt value.</summary>
+    public static DateTime Now => TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, _timeZone);
+}