init

src/client/Microsoft.Identity.Client/Utils/DateTimeHelpers.cs

@@ -63,15 +63,39 @@ public static long GetDurationFromWindowsTimestamp(string windowsTimestampInFutu
             return (long)unixTimestamp - CurrDateTimeInUnixTimestamp();
         }
 
-        public static long GetDurationFromNowInSeconds(string unixTimestampInFuture)
+        public static long GetDurationFromNowInSeconds(string expiresOn)
         {
-            if (string.IsNullOrEmpty(unixTimestampInFuture))
+            if (string.IsNullOrEmpty(expiresOn))
             {
                 return 0;
             }
 
-            long expiresOnUnixTimestamp = long.Parse(unixTimestampInFuture, CultureInfo.InvariantCulture);
-            return expiresOnUnixTimestamp - CurrDateTimeInUnixTimestamp();
+            // First, try to parse as Unix timestamp (number of seconds since epoch)
+            if (long.TryParse(expiresOn, out long expiresOnUnixTimestamp))
+            {
+                return expiresOnUnixTimestamp - DateTimeHelpers.CurrDateTimeInUnixTimestamp();
+            }
+
+            // Try parsing as ISO 8601 
+            if (DateTimeOffset.TryParse(expiresOn, null, DateTimeStyles.RoundtripKind, out DateTimeOffset expiresOnDateTime))
+            {
+                return (long)(expiresOnDateTime - DateTimeOffset.UtcNow).TotalSeconds;
+            }
+
+            // Try RFC 1123 format 
+            if (DateTimeOffset.TryParseExact(expiresOn, "R", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal, out expiresOnDateTime))
+            {
+                return (long)(expiresOnDateTime - DateTimeOffset.UtcNow).TotalSeconds;
+            }
+
+            // Try parsing Unix timestamp in milliseconds 
+            if (long.TryParse(expiresOn, out long expiresOnMillisTimestamp) && expiresOn.Length > 10)
+            {
+                return (expiresOnMillisTimestamp / 1000) - DateTimeHelpers.CurrDateTimeInUnixTimestamp();
+            }
+
+            // If no format works, throw an MSAL client exception
+            throw new MsalClientException("invalid_token_expiration_format", $"Failed to parse Expires On value. Invalid format for expiresOn: '{expiresOn}'.");
         }
 
         public static DateTimeOffset? DateTimeOffsetFromDuration(long? duration)

tests/Microsoft.Identity.Test.Common/Core/Mocks/MockHelpers.cs

@@ -113,9 +113,21 @@ public static string GetBridgedHybridSpaTokenResponse(string spaAccountId)
             ",\"id_token_expires_in\":\"3600\"}";
         }
 
-        public static string GetMsiSuccessfulResponse(int expiresInHours = 1)
+        public static string GetMsiSuccessfulResponse(int expiresInHours = 1, bool useIsoFormat = false)
         {
-            string expiresOn = DateTimeHelpers.DateTimeToUnixTimestamp(DateTime.UtcNow.AddHours(expiresInHours));
+            string expiresOn;
+
+            if (useIsoFormat)
+            {
+                // Return ISO 8601 format
+                expiresOn = DateTime.UtcNow.AddHours(expiresInHours).ToString("o", CultureInfo.InvariantCulture);
+            }
+            else
+            {
+                // Return Unix timestamp format
+                expiresOn = DateTimeHelpers.DateTimeToUnixTimestamp(DateTime.UtcNow.AddHours(expiresInHours));
+            }
+
             return
           "{\"access_token\":\"" + TestConstants.ATSecret + "\",\"expires_on\":\"" + expiresOn + "\",\"resource\":\"https://management.azure.com/\",\"token_type\":" +
           "\"Bearer\",\"client_id\":\"client_id\"}";

tests/Microsoft.Identity.Test.Unit/ManagedIdentityTests/ManagedIdentityTests.cs

@@ -806,10 +806,13 @@ public async Task ManagedIdentityCacheTestAsync()
         }
 
         [DataTestMethod]
-        [DataRow(1, false)]
-        [DataRow(2, false)]
-        [DataRow(3, true)]
-        public async Task ManagedIdentityExpiresOnTestAsync(int expiresInHours, bool refreshOnHasValue)
+        [DataRow(1, false, false)]
+        [DataRow(2, false, false)]
+        [DataRow(3, true, false)]
+        [DataRow(1, false, true)]
+        [DataRow(2, false, true)]
+        [DataRow(3, true, true)]
+        public async Task ManagedIdentityExpiresOnTestAsync(int expiresInHours, bool refreshOnHasValue, bool useIsoFormat)
         {
             using (new EnvVariableContext())
             using (var httpManager = new MockHttpManager(isManagedIdentity: true))

tests/Microsoft.Identity.Test.Unit/UtilTests/DateTimeHelperTests.cs

@@ -0,0 +1,59 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.Identity.Client;
+using Microsoft.Identity.Client.Utils;
+using Microsoft.Identity.Test.Common;
+using Microsoft.Identity.Test.Common.Core.Helpers;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace Microsoft.Identity.Test.Unit.UtilTests
+{
+    [TestClass]
+    public class DateTimeHelperTests
+    {
+        [TestMethod]
+        public void TestGetDurationFromNowInSeconds()
+        {
+            // Arrange
+            var currentTime = DateTimeOffset.UtcNow;
+
+            // Unix timestamp (seconds since epoch)
+            string unixTimestamp = DateTimeHelpers.DateTimeToUnixTimestamp(currentTime);
+            long result = DateTimeHelpers.GetDurationFromNowInSeconds(unixTimestamp);
+            Assert.IsTrue(result >= 0, "Unix timestamp failed");
+
+            // ISO 8601 format
+            string iso8601 = currentTime.ToString("o", CultureInfo.InvariantCulture); // ISO 8601 with "o" format
+            result = DateTimeHelpers.GetDurationFromNowInSeconds(iso8601);
+            Assert.IsTrue(result >= 0, "ISO 8601 failed");
+
+            // RFC 1123 format
+            string rfc1123 = currentTime.ToString("R", CultureInfo.InvariantCulture); // RFC 1123 with "R" format
+            result = DateTimeHelpers.GetDurationFromNowInSeconds(rfc1123);
+            Assert.IsTrue(result >= 0, "RFC 1123 failed");
+
+            // Common format: MM/dd/yyyy HH:mm:ss
+            string commonFormat1 = currentTime.ToString("MM/dd/yyyy HH:mm:ss", CultureInfo.InvariantCulture);
+            result = DateTimeHelpers.GetDurationFromNowInSeconds(commonFormat1);
+            Assert.IsTrue(result >= 0, "Common Format 1 failed");
+
+            // Common format: yyyy-MM-dd HH:mm:ss
+            string commonFormat2 = currentTime.ToString("yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture);
+            result = DateTimeHelpers.GetDurationFromNowInSeconds(commonFormat2);
+            Assert.IsTrue(result >= 0, "Common Format 2 failed");
+
+            // Invalid format: This should throw an MsalClientException
+            string invalidFormat = "invalid-date-format";
+            Assert.ThrowsException<MsalClientException>(() =>
+            {
+                DateTimeHelpers.GetDurationFromNowInSeconds(invalidFormat);
+            });
+        }
+    }
+}