fixed issue with zero-shift timezone and added unit test

Author: Crypt32

Asn1Parser/Universal/Asn1DateTime.cs

@@ -42,13 +42,14 @@ protected Asn1DateTime(Asn1Type type, DateTime time, TimeZoneInfo? zone = null,
     public DateTime Value { get; protected set; }
 
     void m_encode(Asn1Type type, DateTime time, TimeZoneInfo? zone, Boolean preciseTime) {
+        zone = DateTimeUtils.CoerceTimeZone(zone);
         time = zone == null
             ? DateTime.SpecifyKind(time, DateTimeKind.Local)
             : TimeZoneInfo.ConvertTimeToUtc(time, zone).ToLocalTime();
         Value = time;
-        ZoneInfo = zone;
         Boolean utcTime = type == Asn1Type.UTCTime;
-        Initialize(new Asn1Reader(Asn1Utils.Encode(DateTimeUtils.Encode(time, zone, utcTime, preciseTime), type)));
+        Initialize(new Asn1Reader(Asn1Utils.Encode(DateTimeUtils.Encode(time, ref zone, utcTime, preciseTime), type)));
+        ZoneInfo = zone;
     }
     void m_decode(Byte[] rawData) {
         var asn = new Asn1Reader(rawData);

Asn1Parser/Utils/DateTimeUtils.cs

@@ -7,7 +7,7 @@
 namespace SysadminsLV.Asn1Parser.Utils;
 
 static class DateTimeUtils {
-    public static Byte[] Encode(DateTime time, TimeZoneInfo? zone, Boolean UTC, Boolean usePrecise) {
+    public static Byte[] Encode(DateTime time, ref TimeZoneInfo? zone, Boolean UTC, Boolean usePrecise) {
         String suffix = String.Empty;
         String preValue;
         String format = UTC
@@ -19,7 +19,7 @@ public static Byte[] Encode(DateTime time, TimeZoneInfo? zone, Boolean UTC, Bool
             // it was requested. See ITU-T X.690, section 11.7
             suffix += (time.Millisecond / 1000d).ToString(CultureInfo.InvariantCulture).Substring(1);
         }
-        zone = coerceTimeZone(zone);
+        zone = CoerceTimeZone(zone);
         if (zone == null) {
             preValue = time.ToUniversalTime().ToString(format) + suffix + "Z";
         } else {
@@ -48,7 +48,7 @@ public static DateTime Decode(Asn1Reader asn, out TimeZoneInfo? zone) {
         return extractDateTime(SB.ToString(), out zone);
     }
 
-    static TimeZoneInfo? coerceTimeZone(TimeZoneInfo? zone) {
+    public static TimeZoneInfo? CoerceTimeZone(TimeZoneInfo? zone) {
         // if zone is explicitly specified, but its offset against UTC is zero, we do not encode zone.
         if ((zone?.BaseUtcOffset.TotalMinutes ?? 0) == 0) {
             return null;

tests/Asn1Parser.Tests/Asn1DateTimeTests.cs

@@ -15,6 +15,13 @@ public void TestZuluSimple() {
         var gt = new Asn1GeneralizedTime(dt);
         assertDateTimeEncode(Asn1Type.GeneralizedTime, gt, dt, "yyyyMMddHHmmssZ");
     }
+    [TestMethod, Description("Tests explicit zero-shift timezone, must result in Zulu time.")]
+    public void TestUtcTimeZone() {
+        var zone = TimeZoneInfo.FindSystemTimeZoneById("Greenwich Standard Time");
+        var dt = DateTime.ParseExact("2024-08-07 16:12:37", "yyyy-MM-dd HH:mm:ss", null);
+        var gt = new Asn1GeneralizedTime(dt, zone);
+        assertDateTimeEncode(Asn1Type.GeneralizedTime, gt, dt, "yyyyMMddHHmmssZ");
+    }
     [TestMethod, Description("Test date/time with fractions and fraction is zero")]
     public void TestZuluFraction0() {
         var dt = DateTime.ParseExact("2024-08-07 16:12:37.0", "yyyy-MM-dd HH:mm:ss.f", null);