From 092526e65249ca3f98fa89393966087f3e223edc Mon Sep 17 00:00:00 2001
From: tikhonov-ka <tikhonov-ka@yandex-team.com>
Date: Wed, 20 May 2026 20:01:58 +0300
Subject: Fix a local time zone time serialization bug on Windows
 commit_hash:444da85d16474126d9f2373887f85e4601421460

---
 util/datetime/base.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/util/datetime/base.cpp b/util/datetime/base.cpp
index 9148badc829..e3bc1442cf4 100644
--- a/util/datetime/base.cpp
+++ b/util/datetime/base.cpp
@@ -112,7 +112,8 @@ namespace {
         if (GetTimeZoneInformation(&tz) == TIME_ZONE_ID_INVALID) {
             ythrow TSystemError() << "Failed to get the system time zone";
         }
-        i64 utcOffsetInMinutes = -tz.Bias;
+        const LONG seasonalBias = localTime.tm_isdst > 0 ? tz.DaylightBias : tz.StandardBias;
+        i64 utcOffsetInMinutes = -(tz.Bias + seasonalBias);
 #endif
         if (utcOffsetInMinutes == 0) {
             os << 'Z';
-- 
cgit v1.3