case 4682 - automatic backup runs at the chosen time on the server's clock all year

Same fix as AyaNova: the backup ran at the stored UTC hour, so with daylight
saving it moved an hour on the server's clock for part of the year.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/util/ServerGlobalOpsSettingsCache.cs

@@ -51,22 +51,36 @@ namespace Sockeye.Util
         internal static void SetNextBackup()
         {
             DateTime utcNow = DateTime.UtcNow;
+            //case 4682: the backup time is a time on the server's clock; days are the server's local days
+            DateTime localToday = TimeZoneInfo.ConvertTimeFromUtc(utcNow, TimeZoneInfo.Local).Date;
             //Has last backup run more than 24 hours ago?
             if (NextBackup < utcNow.AddHours(-24))
             {
                 //set it to today then
-                NextBackup = new DateTime(utcNow.Year, utcNow.Month, utcNow.Day, Backup.BackupTime.Hour, Backup.BackupTime.Minute, 0, DateTimeKind.Utc);
+                NextBackup = BackupTimeOnLocalDay(localToday);
                 //Make sure next backup is in the future
                 if (NextBackup < utcNow)
-                    NextBackup = NextBackup.AddDays(1);
+                    NextBackup = BackupTimeOnLocalDay(localToday.AddDays(1));
             }
             else
             {
                 //less than 24 hours, set it to tomorrow
-                NextBackup = new DateTime(utcNow.Year, utcNow.Month, utcNow.Day, Backup.BackupTime.Hour, Backup.BackupTime.Minute, 0, DateTimeKind.Utc);
+                NextBackup = BackupTimeOnLocalDay(localToday.AddDays(1));
-                NextBackup = NextBackup.AddDays(1);
             }
         }
 
+        //case 4682: the backup time is stored as the UTC moment it meant on the day it was set, and was run at that UTC hour
+        //every day, so it moved an hour on the server's clock with each daylight saving change. The server's clock time is
+        //recovered with that day's offset and the backup is run at that clock time on the given local day (UTC returned)
+        private static DateTime BackupTimeOnLocalDay(DateTime localDay)
+        {
+            var chosen = TimeZoneInfo.ConvertTimeFromUtc(DateTime.SpecifyKind(Backup.BackupTime, DateTimeKind.Utc), TimeZoneInfo.Local);
+            var local = DateTime.SpecifyKind(localDay.Date + new TimeSpan(chosen.Hour, chosen.Minute, 0), DateTimeKind.Unspecified);
+            //a time skipped when the clocks go forward (e.g. 2:30 AM that night) runs an hour later
+            if (TimeZoneInfo.Local.IsInvalidTime(local))
+                local = local.AddHours(1);
+            return TimeZoneInfo.ConvertTimeToUtc(local, TimeZoneInfo.Local);
+        }
+
     }//eoc
 }//eons