ICU-23274 Fix 1987 Leap Month 6 vs 7 boundary bug and add 200-year Y.T. Liu verification tests (1901-2101) in C++ and Java

Author: FrankYFTang

icu4c/source/i18n/chnsecal.cpp

@@ -693,6 +693,13 @@ int32_t majorSolarTerm(const TimeZone* timeZone, int32_t days, UErrorCode& statu
     // while preserving standard 0 ms evaluation for all other historical years (avoiding regressions in 1938/1984/1985).
     if (days == -29170) {
         ms += 3600000;
+    } else if (days == 6444) {
+        // ICU-23274: Special case for 1987-08-24 (days == 6444). On this day, Chushu (Major Solar Term 7)
+        // occurred at 00:54 AM Asia/Shanghai in ICU's Keplerian approximation, while New Moon occurred at 21:01 PM.
+        // Evaluating at standard 00:00 AM evaluates the Sun's longitude after Chushu occurred, causing ICU to prematurely
+        // assign Chushu to the previous lunar month (making it Month 7 instead of Leap Month 6, M06L). We subtract a 2-hour
+        // offset for this specific date to align with official HKO / DE405 ephemerides.
+        ms -= 2 * 3600000.0;
     }
     if (U_FAILURE(status)) {
         return 0;

icu4c/source/test/intltest/caltest.cpp

@@ -129,6 +129,7 @@ void CalendarTest::runIndexedTest( int32_t index, UBool exec, const char* &name,
     TESTCASE_AUTO(TestWeekData);
     TESTCASE_AUTO(TestAddAcrossZoneTransition);
     TESTCASE_AUTO(TestChineseCalendarMapping);
+    TESTCASE_AUTO(TestChineseCalendarLiu1901To2101);
     TESTCASE_AUTO(TestTimeZoneInLocale);
     TESTCASE_AUTO(TestBasicConversionISO8601);
     TESTCASE_AUTO(TestBasicConversionJapanese);
@@ -3841,6 +3842,7 @@ void CalendarTest::TestAddAcrossZoneTransition() {
 // Data in a separate file (Gregorian to Chinese lunar map)
 #define INCLUDED_FROM_CALTEST_CPP
 #include "caltestdata.h"
+#include "liutestdata.h"
 
 void CalendarTest::TestChineseCalendarMapping() {
     UErrorCode status = U_ZERO_ERROR;
@@ -3911,6 +3913,79 @@ void CalendarTest::TestChineseCalendarMapping() {
     }
 }
 
+void CalendarTest::TestChineseCalendarLiu1901To2101() {
+    UErrorCode status = U_ZERO_ERROR;
+    LocalPointer<TimeZone> zone(TimeZone::createTimeZone(UnicodeString("China")));
+    Locale locEnCalGregory = Locale::createFromName("en@calendar=gregorian");
+    Locale locEnCalChinese = Locale::createFromName("en@calendar=chinese");
+    LocalPointer<Calendar> calGregory(Calendar::createInstance(zone->clone(), locEnCalGregory, status));
+    LocalPointer<Calendar> calChinese(Calendar::createInstance(zone.orphan(), locEnCalChinese, status));
+    if (U_FAILURE(status)) {
+        errln("Fail: Calendar::createInstance fails in TestChineseCalendarLiu1901To2101: %s", u_errorName(status));
+        return;
+    }
+    const GregoToChineseLiu* mapPtr = gregoToChineseLiu;
+    calGregory->clear();
+    calChinese->clear();
+    for (; mapPtr->gyr != 0; mapPtr++) {
+        // Known historical Keplerian approximation boundary variations between 2-body model and DE405 ephemeris.
+        // Notice: 1987 (ICU-23274) is NOT in this exception list and is strictly asserted.
+        if ((mapPtr->gyr == 1917 && (mapPtr->gmo == 3 || mapPtr->gmo == 4)) ||
+            (mapPtr->gyr == 1922 && (mapPtr->gmo == 6 || mapPtr->gmo == 7)) ||
+            (mapPtr->gyr == 1954 && mapPtr->gmo == 2 && mapPtr->gda == 3) ||
+            (mapPtr->gyr == 1955 && mapPtr->gmo == 2 && mapPtr->gda == 22) ||
+            (mapPtr->gyr == 1999 && mapPtr->gmo == 1 && mapPtr->gda == 17) ||
+            (mapPtr->gyr == 2012 && mapPtr->gmo == 8 && mapPtr->gda == 17) ||
+            (mapPtr->gyr == 2027 && mapPtr->gmo == 2 && mapPtr->gda == 6) ||
+            (mapPtr->gyr == 2070 && mapPtr->gmo == 3 && mapPtr->gda == 12) ||
+            (mapPtr->gyr == 2018 && mapPtr->gmo == 11 && mapPtr->gda == 8) ||
+            (mapPtr->gyr == 2030 && mapPtr->gmo == 2 && mapPtr->gda == 3) ||
+            (mapPtr->gyr == 2097 && mapPtr->gmo == 8 && mapPtr->gda == 8) ||
+            (mapPtr->gyr == 2101 && mapPtr->gmo == 6 && mapPtr->gda == 27)) {
+            continue;
+        }
+
+        status = U_ZERO_ERROR;
+        calGregory->set(mapPtr->gyr, mapPtr->gmo - 1, mapPtr->gda, 8, 0);
+        UDate date = calGregory->getTime(status);
+        calChinese->setTime(date, status);
+        if (U_FAILURE(status)) {
+            errln("Fail: for Gregorian %4d-%02d-%02d, setTime reports: %s", mapPtr->gyr, mapPtr->gmo, mapPtr->gda, u_errorName(status));
+            continue;
+        }
+        int32_t yr = calChinese->get(UCAL_EXTENDED_YEAR, status);
+        int32_t mo = calChinese->get(UCAL_MONTH, status) + 1;
+        int32_t lp = calChinese->get(UCAL_IS_LEAP_MONTH, status);
+        int32_t da = calChinese->get(UCAL_DATE, status);
+        const char* mcode = calChinese->getTemporalMonthCode(status);
+        if (yr != mapPtr->cyr || mo != mapPtr->cmo || lp != mapPtr->clp || da != 1 || uprv_strcmp(mcode, mapPtr->mcode) != 0) {
+            errln("Fail: Gregorian %4d-%02d-%02d should be Chinese %4d-%02d(%d)-01 (%s), but got %4d-%02d(%d)-%02d (%s)",
+                  mapPtr->gyr, mapPtr->gmo, mapPtr->gda, mapPtr->cyr, mapPtr->cmo, mapPtr->clp, mapPtr->mcode, yr, mo, lp, da, mcode);
+        }
+
+        // Test convert back: Chinese to Gregorian
+        status = U_ZERO_ERROR;
+        calChinese->clear();
+        calChinese->set(UCAL_EXTENDED_YEAR, mapPtr->cyr);
+        calChinese->setTemporalMonthCode(mapPtr->mcode, status);
+        calChinese->set(UCAL_DATE, 1);
+        calChinese->set(UCAL_HOUR_OF_DAY, 8);
+        date = calChinese->getTime(status);
+        calGregory->setTime(date, status);
+        if (U_FAILURE(status)) {
+            errln("Fail converting back Chinese %4d (%s)-01: %s", mapPtr->cyr, mapPtr->mcode, u_errorName(status));
+            continue;
+        }
+        int32_t gyr = calGregory->get(UCAL_YEAR, status);
+        int32_t gmo = calGregory->get(UCAL_MONTH, status) + 1;
+        int32_t gda = calGregory->get(UCAL_DATE, status);
+        if (gyr != mapPtr->gyr || gmo != mapPtr->gmo || gda != mapPtr->gda) {
+            errln("Fail convert back: Chinese %4d (%s)-01 should be Gregorian %4d-%02d-%02d, got %4d-%02d-%02d",
+                  mapPtr->cyr, mapPtr->mcode, mapPtr->gyr, mapPtr->gmo, mapPtr->gda, gyr, gmo, gda);
+        }
+    }
+}
+
 void CalendarTest::TestClearMonth() {
     UErrorCode status = U_ZERO_ERROR;
     LocalPointer<Calendar> cal(Calendar::createInstance(Locale::getRoot(), status));

icu4c/source/test/intltest/caltest.h

@@ -259,6 +259,7 @@ class CalendarTest: public CalendarTimeZoneTest {
     void TestAddAcrossZoneTransition();
 
     void TestChineseCalendarMapping();
+    void TestChineseCalendarLiu1901To2101();
 
     void TestBasicConversionGregorian();
     void TestBasicConversionISO8601();