diff --git a/icu4c/source/data/misc/metaZones.txt b/icu4c/source/data/misc/metaZones.txt
index 4008abe81559..6e243d7dcaff 100644
--- a/icu4c/source/data/misc/metaZones.txt
+++ b/icu4c/source/data/misc/metaZones.txt
@@ -1261,6 +1261,11 @@ metaZones:table(nofallback){
                 "1990-03-20 22:00",
                 "1994-03-20 22:00",
             }
+            {
+                "Africa_Western",
+                "1994-03-20 22:00",
+                "2017-10-23 22:00",
+            }
             {
                 "Africa_Central",
                 "2017-10-23 22:00",
@@ -3837,6 +3842,18 @@ metaZones:table(nofallback){
                 "Europe_Central",
             }
         }
+        "Europe:Dublin"{
+            {
+                "Irish",
+                "1970-01-01 00:00",
+                "1971-10-31 02:00",
+            }
+            {
+                "GMT",
+                "1971-10-31 02:00",
+                "9999-12-31 23:59",
+            }
+        }
         "Europe:Gibraltar"{
             {
                 "Europe_Central",
diff --git a/icu4c/source/test/intltest/tztest.cpp b/icu4c/source/test/intltest/tztest.cpp
index 988a5af21dc5..eaa719cb53b6 100644
--- a/icu4c/source/test/intltest/tztest.cpp
+++ b/icu4c/source/test/intltest/tztest.cpp
@@ -2395,9 +2395,16 @@ static struct   {
 
       // Repeating the test data for DST.  The test data below trigger the problem reported
       // by Ticket#6644
+      {"Europe/London",       "en", false, TimeZone::SHORT, "GMT" /*"BST"*/},
+      {"Europe/London",       "en", false, TimeZone::LONG,  "Greenwich Mean Time"},
       {"Europe/London",       "en", true, TimeZone::SHORT, "GMT+1" /*"BST"*/},
       {"Europe/London",       "en", true, TimeZone::LONG,  "British Summer Time"},
 
+      {"Europe/Dublin",       "en", false, TimeZone::SHORT, "GMT" /*"IST"*/},
+      {"Europe/Dublin",       "en", false, TimeZone::LONG,  "Greenwich Mean Time"},
+      {"Europe/Dublin",       "en", true, TimeZone::SHORT, "GMT+1" /*"IST"*/},
+      {"Europe/Dublin",       "en", true, TimeZone::LONG,  "Irish Standard Time"},
+
       {nullptr, nullptr, false, TimeZone::SHORT, nullptr}   // nullptr values terminate list
     };
 
diff --git a/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/TimeZoneFormatTest.java b/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/TimeZoneFormatTest.java
index aba8730011c8..f1d23f0260eb 100644
--- a/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/TimeZoneFormatTest.java
+++ b/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/TimeZoneFormatTest.java
@@ -946,6 +946,15 @@ public void TestFormat() {
                 "\u65E5\u672C\u6A19\u6E96\u6642",   // "日本標準時"
                 TimeType.UNKNOWN
             },
+            // Regression test for ICU-23278
+            {
+                "en",
+                "Europe/Dublin",
+                dateJan,
+                Style.SPECIFIC_LONG,
+                "Greenwich Mean Time",
+                TimeType.STANDARD
+            }
         };
 
         for (Object[] testCase : TESTDATA) {
diff --git a/icu4j/main/core/src/main/resources/com/ibm/icu/impl/data/icudata/metaZones.res b/icu4j/main/core/src/main/resources/com/ibm/icu/impl/data/icudata/metaZones.res
index 9e51304776a6..e525fc1d1d21 100644
Binary files a/icu4j/main/core/src/main/resources/com/ibm/icu/impl/data/icudata/metaZones.res and b/icu4j/main/core/src/main/resources/com/ibm/icu/impl/data/icudata/metaZones.res differ
diff --git a/tools/cldr/cldr-to-icu/src/main/resources/ldml2icu_supplemental.txt b/tools/cldr/cldr-to-icu/src/main/resources/ldml2icu_supplemental.txt
index 6163d4b16b3f..3c0a5b5289ed 100644
--- a/tools/cldr/cldr-to-icu/src/main/resources/ldml2icu_supplemental.txt
+++ b/tools/cldr/cldr-to-icu/src/main/resources/ldml2icu_supplemental.txt
@@ -319,14 +319,13 @@
 # metaZones.xml - metaZones.txt
 //supplementalData/metaZones/mapTimezones[@type="metazones"]/mapZone[@type="(%A)"][@other="(%W)"][@territory="(%W)"] ; /mapTimezones/$2/$3 ; values=$1
 //supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@mzone="(%W)"] ; /metazoneInfo/"$1"/<$2> ; values=$2
-# For the from/to entries, ignore any stdOffset/dstOffset values for now, see CLDR-18880.
-# Aalso note the path ordering of  stdOffset/dstOffset vs mzone is odd, filed CLDR-18921 about that.
 //supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@from="(%A)"][@mzone="(%W)"] ; /metazoneInfo/"$1"/<$2> ; values=$3 "$2" "9999-12-31 23:59"
 //supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@from="(%A)"][@to="(%A)"][@mzone="(%W)"] ; /metazoneInfo/"$1"/<$2> ; values=$4 "$2" "$3"
 //supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@to="(%A)"][@mzone="(%W)"] ; /metazoneInfo/"$1"/<1970-01-01 00:00> ; values=$3 "1970-01-01 00:00" "$2"
-//supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@from="(%A)"][@stdOffset="(%A)"][@dstOffset="(%A)"][@mzone="(%W)"] ; /metazoneInfo/"$1"/<$2> ; values=$5 "$2" "9999-12-31 23:59"
-//supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@from="(%A)"][@to="(%A)"][@stdOffset="(%A)"][@dstOffset="(%A)"][@mzone="(%W)"] ; /metazoneInfo/"$1"/<$2> ; values=$6 "$2" "$3"
-//supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@to="(%A)"][@stdOffset="(%A)"][@dstOffset="(%A)"][@mzone="(%W)"] ; /metazoneInfo/"$1"/<1970-01-01 00:00> ; values=$5 "1970-01-01 00:00" "$2"
+# Ignore any stdOffset/dstOffset values for now, see CLDR-18880.
+//supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@from="(%A)"][@mzone="(%W)"][@stdOffset="(%A)"][@dstOffset="(%A)"] ; /metazoneInfo/"$1"/<$2> ; values=$3 "$2" "9999-12-31 23:59"
+//supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@from="(%A)"][@to="(%A)"][@mzone="(%W)"][@stdOffset="(%A)"][@dstOffset="(%A)"] ; /metazoneInfo/"$1"/<$2> ; values=$4 "$2" "$3"
+//supplementalData/metaZones/metazoneInfo/timezone[@type="(%W)"]/usesMetazone[@to="(%A)"][@mzone="(%W)"][@stdOffset="(%A)"][@dstOffset="(%A)"] ; /metazoneInfo/"$1"/<1970-01-01 00:00> ; values=$3 "1970-01-01 00:00" "$2"
 #
 //supplementalData/metaZones/metazoneIds/metazoneId[@shortId="(%A)"][@longId="(%A)"][@deprecated="false"] ; /metazoneIds/$1 ; values=$2