From b7304d8b85bcb7bdfaf51c4d64a7a4075734d32c Mon Sep 17 00:00:00 2001
From: Jeff Genovy <29107334+jefgen@users.noreply.github.com>
Date: Thu, 21 Feb 2019 21:50:38 -0800
Subject: [PATCH] ICU-20482 Windows component version should be conditional on
 the new era date.

cherry-picked from: 1775e4c773244d874e93b549115250d42bb2c5a1
---
 icu4c/source/i18n/japancal.cpp | 44 +++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 16 deletions(-)

diff --git a/icu4c/source/i18n/japancal.cpp b/icu4c/source/i18n/japancal.cpp
index 720bf130b4a..6d19a9ac016 100644
--- a/icu4c/source/i18n/japancal.cpp
+++ b/icu4c/source/i18n/japancal.cpp
@@ -81,6 +81,8 @@ static void U_CALLCONV initializeEras(UErrorCode &status) {
 
 // When ICU is used as a Windows system component, we want to use the NLS registry key, so that
 // enabling the tentative era for NLS also enables it for ICU.
+//
+// NOTE: The code inside the #ifdef below can be removed after the transition date.
 #ifdef ICU_DATA_DIR_WINDOWS
     // Look in the registry key and enable tentative era if there are more than 4 era values.
     HKEY hkeyJapaneseEras = nullptr;
@@ -90,28 +92,38 @@ static void U_CALLCONV initializeEras(UErrorCode &status) {
         KEY_QUERY_VALUE,
         &hkeyJapaneseEras) == ERROR_SUCCESS)
     {
-        DWORD cValues; // number of values for key 
+        DWORD cValues; // number of values for key
 
         // Query number of values
         DWORD retVal = RegQueryInfoKeyW(
             hkeyJapaneseEras,
-            nullptr,         
-            nullptr,         
-            nullptr,         
-            nullptr,         
-            nullptr,         
-            nullptr,         
-            &cValues,         
-            nullptr,         
-            nullptr,         
-            nullptr,         
-            nullptr);        
+            nullptr,
+            nullptr,
+            nullptr,
+            nullptr,
+            nullptr,
+            nullptr,
+            &cValues,
+            nullptr,
+            nullptr,
+            nullptr,
+            nullptr);
 
         if (retVal == ERROR_SUCCESS)
         {
             if (cValues > 4)
             {
-                includeTentativeEra = TRUE;
+                // The start date for the Eras comes from the ICU/CLDR data file.
+                // Currently there is only one 'new' era in the file with the start date of 2019-05-01.
+                //
+                // The check below ensures that even if the new era NLS registry key is present, we
+                // do not "enable" the new era until the actual date of the transition.
+                SYSTEMTIME time = {};
+                GetLocalTime(&time);
+                if ((time.wYear > 2019) || ((time.wYear == 2019) && (time.wMonth >= 5)))
+                {
+                    includeTentativeEra = TRUE;
+                }
             }
         }
 
@@ -185,7 +197,7 @@ const char *JapaneseCalendar::getType() const
     return "japanese";
 }
 
-int32_t JapaneseCalendar::getDefaultMonthInYear(int32_t eyear) 
+int32_t JapaneseCalendar::getDefaultMonthInYear(int32_t eyear)
 {
     int32_t era = internalGetEra();
     // TODO do we assume we can trust 'era'?  What if it is denormalized?
@@ -206,7 +218,7 @@ int32_t JapaneseCalendar::getDefaultMonthInYear(int32_t eyear)
     return month;
 }
 
-int32_t JapaneseCalendar::getDefaultDayInMonth(int32_t eyear, int32_t month) 
+int32_t JapaneseCalendar::getDefaultDayInMonth(int32_t eyear, int32_t month)
 {
     int32_t era = internalGetEra();
     int32_t day = 1;
@@ -265,7 +277,7 @@ void JapaneseCalendar::handleComputeFields(int32_t julianDay, UErrorCode& status
 }
 
 /*
-Disable pivoting 
+Disable pivoting
 */
 UBool JapaneseCalendar::haveDefaultCentury() const
 {
-- 
2.40.0