(arrow) branch main updated: GH-47131: [C#] Fix day off by 1 in Date64Array (#47132)

[curth]

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The following commit(s) were added to refs/heads/main by this push:
     new fc6b4b09cb GH-47131: [C#] Fix day off by 1 in Date64Array (#47132)
fc6b4b09cb is described below

commit fc6b4b09cb68e726252242a12fc381e8fcbebf37
Author: jeremycostanzo <56163564+jeremycosta...@users.noreply.github.com>
AuthorDate: Tue Jul 22 05:47:06 2025 +0200

    GH-47131: [C#] Fix day off by 1 in Date64Array (#47132)
    
    ### Rationale for this change
    `Date64Array.Convert(DateTimeOffset)` substracts one day on date times that 
are at 00:00 am and < 1970.
    For example, 01/01/1969 00:00:00 gets converted to 12/31/1968 whereas the 
expected result is 01/01/1969.
    
    ### What changes are included in this PR?
    Fix to the described bug.
    
    ### Are these changes tested?
    Yes
    
    ### Are there any user-facing changes?
    No
    
    **This PR contains a "Critical Fix".**
    * GitHub Issue: #47131
    
    Authored-by: Jeremy Costanzo <jeremy.costa...@pigment.com>
    Signed-off-by: Curt Hagenlocher <c...@hagenlocher.org>
---
 csharp/src/Apache.Arrow/Arrays/Date64Array.cs         | 7 +------
 csharp/test/Apache.Arrow.Tests/TestDateAndTimeData.cs | 2 +-
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/csharp/src/Apache.Arrow/Arrays/Date64Array.cs 
b/csharp/src/Apache.Arrow/Arrays/Date64Array.cs
index 77538ce59f..bf53574574 100644
--- a/csharp/src/Apache.Arrow/Arrays/Date64Array.cs
+++ b/csharp/src/Apache.Arrow/Arrays/Date64Array.cs
@@ -65,12 +65,7 @@ namespace Apache.Arrow
 
             protected override long Convert(DateTimeOffset dateTimeOffset)
             {
-                // The internal value stored for a DateTimeOffset can be 
thought of as the number of milliseconds,
-                // in multiples of 86400000, that have passed since the UNIX 
epoch.  It is not the same as what would
-                // result from encoding the date from the DateTimeOffset.Date 
property.
-                long millis = dateTimeOffset.ToUnixTimeMilliseconds();
-                long days = millis / MillisecondsPerDay;
-                return (millis < 0 ? days - 1 : days) * MillisecondsPerDay;
+                return new DateTimeOffset(dateTimeOffset.UtcDateTime.Date, 
TimeSpan.Zero).ToUnixTimeMilliseconds();
             }
 
 #if NET6_0_OR_GREATER
diff --git a/csharp/test/Apache.Arrow.Tests/TestDateAndTimeData.cs 
b/csharp/test/Apache.Arrow.Tests/TestDateAndTimeData.cs
index c258fdd2d6..8a8f76bf69 100644
--- a/csharp/test/Apache.Arrow.Tests/TestDateAndTimeData.cs
+++ b/csharp/test/Apache.Arrow.Tests/TestDateAndTimeData.cs
@@ -36,7 +36,7 @@ namespace Apache.Arrow.Tests
 
         private static readonly TimeSpan[] _exampleTimes =
         {
-            new TimeSpan(0, 0, 1), new TimeSpan(12, 0, 0), new TimeSpan(23, 
59, 59),
+            new TimeSpan(0, 0, 0), new TimeSpan(0, 0, 1), new TimeSpan(12, 0, 
0), new TimeSpan(23, 59, 59),
         };
 
         private static readonly DateTimeKind[] _exampleKinds =