diff --git a/NewLife.Core/Common/Utility.cs b/NewLife.Core/Common/Utility.cs
index 0269178bd..74fad9f0e 100644
--- a/NewLife.Core/Common/Utility.cs
+++ b/NewLife.Core/Common/Utility.cs
@@ -91,13 +91,13 @@ public static class Utility
     /// <returns></returns>
     public static DateTimeOffset ToDateTimeOffset(this Object? value, DateTimeOffset defaultValue) => Convert.ToDateTimeOffset(value, defaultValue);
 
-    /// <summary>去掉时间日期指定位置后面部分，可指定毫秒ms、秒s、分m、小时h</summary>
+    /// <summary>去掉时间日期指定位置后面部分，可指定毫秒ms、秒s、分m、小时h、纳秒ns</summary>
     /// <param name="value">时间日期</param>
     /// <param name="format">格式字符串，默认s格式化到秒，ms格式化到毫秒</param>
     /// <returns></returns>
     public static DateTime Trim(this DateTime value, String format = "s") => Convert.Trim(value, format);
 
-    /// <summary>去掉时间日期指定位置后面部分，可指定毫秒ms、秒s、分m、小时h</summary>
+    /// <summary>去掉时间日期指定位置后面部分，可指定毫秒ms、秒s、分m、小时h、纳秒ns</summary>
     /// <param name="value">时间日期</param>
     /// <param name="format">格式字符串，默认s格式化到秒，ms格式化到毫秒</param>
     /// <returns></returns>
@@ -556,7 +556,7 @@ public virtual DateTime ToDateTime(Object? value, DateTime defaultValue)
 
             // 处理UTC
             var utc = false;
-            if (str.EndsWithIgnoreCase(" UTC"))
+            if (str.EndsWithIgnoreCase(" UTC") || str.EndsWith("Z") && str.Contains('T'))
             {
                 utc = true;
                 str = str[0..^4];
@@ -702,7 +702,7 @@ private static Int32 TrimNumber(ReadOnlySpan<Char> input, Span<Char> output)
         return idx;
     }
 
-    /// <summary>去掉时间日期指定位置后面部分，可指定毫秒ms、秒s、分m、小时h</summary>
+    /// <summary>去掉时间日期指定位置后面部分，可指定毫秒ms、秒s、分m、小时h、纳秒ns</summary>
     /// <param name="value">时间日期</param>
     /// <param name="format">格式字符串，默认s格式化到秒，ms格式化到毫秒</param>
     /// <returns></returns>
@@ -712,6 +712,7 @@ public virtual DateTime Trim(DateTime value, String format)
         {
 #if NET7_0_OR_GREATER
             "us" => new DateTime(value.Year, value.Month, value.Day, value.Hour, value.Minute, value.Second, value.Millisecond, value.Microsecond, value.Kind),
+            "ns" => new DateTime(value.Year, value.Month, value.Day, value.Hour, value.Minute, value.Second, value.Millisecond, value.Microsecond / 100 * 100, value.Kind),
 #endif
             "ms" => new DateTime(value.Year, value.Month, value.Day, value.Hour, value.Minute, value.Second, value.Millisecond, value.Kind),
             "s" => new DateTime(value.Year, value.Month, value.Day, value.Hour, value.Minute, value.Second, value.Kind),
diff --git a/XUnitTest.Core/Common/UtilityTests.cs b/XUnitTest.Core/Common/UtilityTests.cs
index 1a4fa6f0f..916ac45d0 100644
--- a/XUnitTest.Core/Common/UtilityTests.cs
+++ b/XUnitTest.Core/Common/UtilityTests.cs
@@ -13,13 +13,26 @@ public void BasicTest()
         Assert.Equal(DateTimeKind.Local, dt.Kind);
         Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss"), dt.ToFullString());
         Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss.fff"), dt.ToFullString(true));
+
         var dt_ = new DateTime(dt.Year, dt.Month, dt.Day, dt.Hour, dt.Minute, dt.Second);
+        Assert.Equal(DateTimeKind.Unspecified, dt_.Kind);
         Assert.Equal(dt.Trim(), dt_);
-        Assert.Equal(dt.Trim(), dt.ToFullString().ToDateTime());
-        Assert.Equal(dt.Trim(), dt.ToInt().ToDateTime());
+
+        var dt2 = dt.ToFullString().ToDateTime();
+        Assert.Equal(DateTimeKind.Unspecified, dt2.Kind);
+        Assert.Equal(dt.Trim(), dt2);
+
+        dt2 = dt.ToInt().ToDateTime();
+        Assert.Equal(DateTimeKind.Unspecified, dt2.Kind);
+        Assert.Equal(dt.Trim(), dt2);
+
+        dt2 = dt.ToLong().ToDateTime();
+        Assert.Equal(DateTimeKind.Unspecified, dt2.Kind);
         Assert.Equal(dt.Trim("ms"), dt.ToLong().ToDateTime());
-        Assert.Equal(dt.Trim("m"), dt.ToInt().ToDateTime().AddSeconds(-dt.Second));
-        Assert.Equal(dt.Trim("h"), dt.ToInt().ToDateTime().AddSeconds(-dt.Second).AddMinutes(-dt.Minute));
+
+        dt2 = dt.ToInt().ToDateTime();
+        Assert.Equal(dt.Trim("m"), dt2.AddSeconds(-dt2.Second));
+        Assert.Equal(dt.Trim("h"), dt2.AddSeconds(-dt2.Second).AddMinutes(-dt2.Minute));
         Assert.Empty(DateTime.MinValue.ToFullString(""));
         Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss"), dt.ToString("", ""));
         Assert.Empty(DateTime.MinValue.ToString("", ""));
@@ -29,7 +42,49 @@ public void BasicTest()
         var dtU = str.ToDateTime();
         Assert.Equal(dt, dtU);
         Assert.Equal(dt.Kind, dtU.Kind);
+    }
+
+    [Fact]
+    public void UtcTest()
+    {
+        var dt = DateTime.UtcNow;
+        Assert.Equal(DateTimeKind.Utc, dt.Kind);
+        Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss"), dt.ToFullString());
+        Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss.fff"), dt.ToFullString(true));
+
+        var dt_ = new DateTime(dt.Year, dt.Month, dt.Day, dt.Hour, dt.Minute, dt.Second, DateTimeKind.Utc);
+        Assert.Equal(DateTimeKind.Utc, dt_.Kind);
+        Assert.Equal(dt.Trim(), dt_);
+
+        var dt2 = dt.ToFullString().ToDateTime();
+        Assert.Equal(DateTimeKind.Unspecified, dt2.Kind);
+        Assert.Equal(dt.Trim(), dt2);
 
+        dt2 = dt.ToInt().ToDateTime();
+        Assert.Equal(DateTimeKind.Unspecified, dt2.Kind);
+        Assert.Equal(dt.Trim(), dt2);
+
+        dt2 = dt.ToLong().ToDateTime();
+        Assert.Equal(DateTimeKind.Unspecified, dt2.Kind);
+        Assert.Equal(dt.Trim("ms"), dt.ToLong().ToDateTime());
+
+        dt2 = dt.ToInt().ToDateTime();
+        Assert.Equal(dt.Trim("m"), dt2.AddSeconds(-dt2.Second));
+        Assert.Equal(dt.Trim("h"), dt2.AddSeconds(-dt2.Second).AddMinutes(-dt2.Minute));
+        Assert.Empty(DateTime.MinValue.ToFullString(""));
+        Assert.Equal(dt.ToString("yyyy-MM-dd HH:mm:ss"), dt.ToString("", ""));
+        Assert.Empty(DateTime.MinValue.ToString("", ""));
+
+        var str = dt.ToString("O");
+        XTrace.WriteLine(str);
+        var dtU = str.ToDateTime();
+        Assert.Equal(dt.Trim("ns"), dtU);
+        Assert.Equal(dt.Kind, dtU.Kind);
+    }
+
+    [Fact]
+    public void TimeZoneInfoTest()
+    {
         var dto = DateTimeOffset.Now;
         Assert.Equal(dto.ToString("yyyy-MM-dd HH:mm:ss zzz"), dto.ToFullString());
         Assert.Equal(dto.ToString("yyyy-MM-dd HH:mm:ss.fff zzz"), dto.ToFullString(true));
@@ -111,6 +166,19 @@ public void DateTimeTest()
         str = "2022/4/6";
         dt = str.ToDateTime();
         Assert.Equal(new DateTime(2022, 4, 6), dt);
+
+        var dt1970 = new DateTime(1970, 1, 1);
+        var dt1970b = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+
+        // DateTime 改变时区后再相减，结果改变；而 DateTimeOffset 不会
+        // DateTime 减去目标时间，忽略目标时区，直接减去时间值
+        dt = DateTime.UtcNow;
+        var n1 = (Int32)(dt - dt1970).TotalSeconds;
+        var n2 = (Int32)(dt.ToLocalTime() - dt1970).TotalSeconds;
+        var n3 = (Int32)(dt - dt1970b).TotalSeconds;
+        var n4 = (Int32)(dt.ToLocalTime() - dt1970b).TotalSeconds;
+        Assert.Equal(n1, n3);
+        Assert.Equal(n2, n4);
     }
 
     [Fact]
@@ -123,6 +191,18 @@ public void DateTimeOffsetTest()
         str = "2020-03-09T21:16:25.9052764+08:00";
         var df = str.ToDateTimeOffset();
         Assert.Equal(new DateTimeOffset(2020, 3, 9, 21, 16, 25, 905, TimeSpan.FromHours(8)).AddTicks(2764), df);
+
+        var dt1970 = new DateTimeOffset(new DateTime(1970, 1, 1));
+        var dt1970b = new DateTimeOffset(new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc));
+
+        // DateTimeOffset 可以改变时区后再相减，结果不变
+        var dto = DateTimeOffset.UtcNow;
+        var n1 = (Int32)(dto - dt1970).TotalSeconds;
+        var n2 = (Int32)(dto.ToLocalTime() - dt1970).TotalSeconds;
+        var n3 = (Int32)(dto - dt1970b).TotalSeconds;
+        var n4 = (Int32)(dto.ToLocalTime() - dt1970b).TotalSeconds;
+        Assert.Equal(n1, n2);
+        Assert.Equal(n3, n4);
     }
 
     [Fact]