Fix ServerStatus.DateTime crashing when the server DateTime format di…

…ffers from the client format (e.g. US vs UK time format)

src/PrtgAPI.Tests.UnitTests/CSharp/BaseTest.cs

@@ -1,7 +1,9 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using PrtgAPI.Reflection;
 using PrtgAPI.Tests.UnitTests.Support.TestItems;
@@ -109,6 +111,22 @@ protected T Execute<T>(Func<PrtgClient, T> action)
             return action(client);
         }
 
+        protected void TestCustomCulture(Action action, CultureInfo newCulture)
+        {
+            var originalCulture = Thread.CurrentThread.CurrentCulture;
+
+            try
+            {
+                Thread.CurrentThread.CurrentCulture = newCulture;
+
+                action();
+            }
+            finally
+            {
+                Thread.CurrentThread.CurrentCulture = originalCulture;
+            }
+        }
+
         private AddressValidatorResponse GetValidator(object urls, Dictionary<Content, int> countOverride, Dictionary<Content, BaseItem[]> itemOverride)
         {
 #pragma warning disable 618

src/PrtgAPI.Tests.UnitTests/CSharp/ObjectData/ServerStatusTests.cs

@@ -1,4 +1,6 @@
-using System.Threading.Tasks;
+using System;
+using System.Globalization;
+using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using PrtgAPI.Tests.UnitTests.Support.TestItems;
 using PrtgAPI.Tests.UnitTests.Support.TestResponses;
@@ -123,6 +125,121 @@ public async Task ServerStatus_ReadOnlyAsync()
             AssertEx.AllPropertiesRetrieveValues(result);
         }
 
+        [UnitTest]
+        [TestMethod]
+        public void ServerStatus_DateTime_ServerUS_ClientUK()
+        {
+            //There's a legal mismatch, so we get the dates backwards
+            TestClockSmallDate(
+                "MM/d/yyyy",
+                "en-GB",
+                expectedClientMonth: 12,
+                expectedClientDay: 1
+            );
+
+            //There's an illegal mismatch, so we reparse the DateTime using US heuristics
+            TestClockLargeDate(
+                "MM/d/yyyy",
+                "en-GB",
+                expectedClientMonth: 1,
+                expectedClientDay: 13
+            );
+        }
+
+        [UnitTest]
+        [TestMethod]
+        public void ServerStatus_DateTime_ServerUS_ClientUS()
+        {
+            TestClockSmallDate(
+                "MM/d/yyyy",
+                "en-US",
+                expectedClientMonth: 1,
+                expectedClientDay: 12
+            );
+
+            TestClockLargeDate(
+                "MM/d/yyyy",
+                "en-US",
+                expectedClientMonth: 1,
+                expectedClientDay: 13
+            );
+        }
+
+        [UnitTest]
+        [TestMethod]
+        public void ServerStatus_DateTime_ServerUK_ClientUS()
+        {
+            //There's a legal mismatch, so we get the dates backwards
+            TestClockSmallDate(
+                "dd/MM/yyyy",
+                "en-US",
+                expectedClientMonth: 12,
+                expectedClientDay: 1
+            );
+
+            //There's an illegal mismatch, so we reparse the DateTime using US heuristics
+            TestClockLargeDate(
+                "dd/MM/yyyy",
+                "en-US",
+                expectedClientMonth: 1,
+                expectedClientDay: 13
+            );
+        }
+
+        [UnitTest]
+        [TestMethod]
+        public void ServerStatus_DateTime_ServerUK_ClientUK()
+        {
+            TestClockSmallDate(
+                "dd/MM/yyyy",
+                "en-GB",
+                expectedClientMonth: 1,
+                expectedClientDay: 12
+            );
+
+            TestClockLargeDate(
+                "dd/MM/yyyy",
+                "en-GB",
+                expectedClientMonth: 1,
+                expectedClientDay: 13
+            );
+        }
+
+        private void TestClockSmallDate(
+            string serverDateFormat,
+            string clientCulture,
+            int expectedClientMonth,
+            int expectedClientDay)
+        {
+            var serverTime = new DateTime(2020, 1, 12, 4, 10, 20, DateTimeKind.Utc).ToLocalTime().ToString($"{serverDateFormat} h:mm:ss tt");
+
+            TestClock(serverTime, clientCulture, new DateTime(2020, expectedClientMonth, expectedClientDay, 4, 10, 20, DateTimeKind.Utc));
+        }
+
+        private void TestClockLargeDate(
+            string serverDateFormat,
+            string clientCulture,
+            int expectedClientMonth,
+            int expectedClientDay)
+        {
+            var serverTime = new DateTime(2020, 1, 13, 4, 10, 20, DateTimeKind.Utc).ToLocalTime().ToString($"{serverDateFormat} h:mm:ss tt");
+
+            TestClock(serverTime, clientCulture, new DateTime(2020, expectedClientMonth, expectedClientDay, 4, 10, 20, DateTimeKind.Utc));
+        }
+
+        private void TestClock(string serverTime, string clientCulture, DateTime expectedInvariantUtc)
+        {
+            var client = Initialize_Client(new ServerStatusResponse(new ServerStatusItem(clock: serverTime)));
+
+            TestCustomCulture(() =>
+            {
+                var now = DateTime.Now.ToString();
+
+                var status = client.GetStatus();
+                Assert.AreEqual(expectedInvariantUtc, status.DateTime.ToUniversalTime());
+            }, CultureInfo.GetCultureInfo(clientCulture));
+        }
+
         public ServerStatusItem GetItem() => new ServerStatusItem();
     }
 }

src/PrtgAPI.Tests.UnitTests/CSharp/ObjectManipulation/SetObjectPropertyTests.cs

@@ -872,22 +872,6 @@ public void SetObjectProperty_DecimalPoint_EuropeanCulture()
             }, new CultureInfo("de-DE"));
         }
 
-        private void TestCustomCulture(Action action, CultureInfo newCulture)
-        {
-            var originalCulture = Thread.CurrentThread.CurrentCulture;
-
-            try
-            {
-                Thread.CurrentThread.CurrentCulture = newCulture;
-
-                action();
-            }
-            finally
-            {
-                Thread.CurrentThread.CurrentCulture = originalCulture;
-            }
-        }
-
         #endregion
         #region Multiple
 

src/PrtgAPI/Objects/Models/ServerStatus.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Globalization;
 using System.Runtime.Serialization;
 using PrtgAPI.Request.Serialization;
 using PrtgAPI.Utilities;
@@ -18,14 +19,32 @@ public class ServerStatus
         private DateTime? clock;
 
         /// <summary>
-        /// Current system time on the PRTG Core Server.
+        /// Current system time on the PRTG Core Server.<para/>
+        /// Note that if the DateTime format of the PRTG Server's language region does not match the DateTime format of the
+        /// system running PrtgAPI,<para/>
+        /// the DateTime format of the value parsed by this property may have months and dates back to front.
         /// </summary>
         public DateTime DateTime
         {
             get
             {
                 if (clock == null)
-                    clock = DateTime.Parse(clockStr);
+                {
+                    //Try and parse the remote DateTime based on the DateTime of the local system. If that fails, we have no idea whether the remote
+                    //system was dd/MM/yyyy or MM/dd/yyyy so just try both. We might not be right if we're on the 1st-12th of the month,
+                    //but it's the best we can do with an ambiguous date format.
+                    DateTime temp;
+
+                    var ukCulture = CultureInfo.GetCultureInfo("en-GB").DateTimeFormat;
+                    var usCulture = CultureInfo.GetCultureInfo("en-US").DateTimeFormat;
+
+                    if (DateTime.TryParse(clockStr, out temp))
+                        clock = temp;
+                    else if (DateTime.TryParse(clockStr, ukCulture, DateTimeStyles.None, out temp))
+                        clock = temp;
+                    else
+                        clock = DateTime.Parse(clockStr, usCulture);
+                }
 
                 return clock.Value;
             }
@@ -154,7 +173,7 @@ public string UserId
         private string userTimeZone;
 
         /// <summary>
-        /// UTC offset of your PRTG Server's timezone.
+        /// UTC offset or name of your PRTG Server's timezone.
         /// </summary>
         [DataMember(Name = "UserTimeZone")]
         public string UserTimeZone