Added extension for ISO 8601 date-time format

test/Cloudflare.Tests/Extensions/DateTimeExtensionsTest.cs

@@ -0,0 +1,50 @@
+using AMWD.Net.Api.Cloudflare;
+
+namespace Cloudflare.Tests.Extensions
+{
+	[TestClass]
+	public class DateTimeExtensionsTest
+	{
+		private const string Format = "yyyy-MM-dd'T'HH:mm:ss'Z'";
+
+		[TestMethod]
+		public void ShouldReturnIsoStringForUtc()
+		{
+			// Arrange
+			var dateTime = new DateTime(2025, 10, 10, 1, 2, 3, DateTimeKind.Utc);
+
+			// Act
+			string isoString = dateTime.ToIso8601Format();
+
+			// Assert
+			Assert.AreEqual(dateTime.ToString(Format), isoString);
+		}
+
+		[TestMethod]
+		public void ShouldReturnIsoStringForUnspecified()
+		{
+			// Arrange
+			var dateTime = new DateTime(2025, 10, 10, 1, 2, 3, DateTimeKind.Unspecified);
+
+			// Act
+			string isoString = dateTime.ToIso8601Format();
+
+			// Assert
+			Assert.AreEqual(dateTime.ToString(Format), isoString);
+		}
+
+		[TestMethod]
+		public void ShouldReturnIsoStringForLocal()
+		{
+			// Arrange
+			var dateTime = new DateTime(2025, 10, 10, 1, 2, 3, DateTimeKind.Local);
+			var offset = TimeZoneInfo.Local.GetUtcOffset(dateTime);
+
+			// Act
+			string isoString = dateTime.ToIso8601Format();
+
+			// Assert
+			Assert.AreEqual(dateTime.Subtract(offset).ToString(Format), isoString);
+		}
+	}
+}