CLDR-18880 Add metazone variant overrides to match rearguard (#4991)

Author: robertbastian

common/dtd/ldmlSupplemental.dtd

@@ -994,6 +994,12 @@ CLDR data files are interpreted according to the LDML specification (http://unic
     <!--@MATCH:time/yyyy-MM-dd HH:mm-->
 <!ATTLIST usesMetazone to CDATA #IMPLIED >
     <!--@MATCH:time/yyyy-MM-dd HH:mm-->
+<!ATTLIST usesMetazone stdOffset CDATA #IMPLIED >
+    <!--@MATCH:regex/[+-][0-9]{2}(:[0-9]{2})?-->
+    <!--@VALUE-->
+<!ATTLIST usesMetazone dstOffset CDATA #IMPLIED >
+    <!--@MATCH:regex/[+-][0-9]{2}(:[0-9]{2})?-->
+    <!--@VALUE-->
 <!ATTLIST usesMetazone mzone NMTOKEN #REQUIRED >
     <!--@MATCH:metazone-->
     <!--@VALUE-->

common/supplemental/metaZones.xml

@@ -187,7 +187,7 @@ For terms of use, see http://www.unicode.org/copyright.html
 			<timezone type="Africa/Windhoek">
 				<usesMetazone to="1990-03-20 22:00" mzone="Africa_Southern"/>
 				<usesMetazone to="1994-03-20 22:00" from="1990-03-20 22:00" mzone="Africa_Central"/>
-				<usesMetazone to="2017-10-23 22:00" from="1994-03-20 22:00" mzone="Africa_Western"/>
+				<usesMetazone to="2017-10-23 22:00" from="1994-03-20 22:00" mzone="Africa_Western" stdOffset="+01" dstOffset="+02"/>
 				<usesMetazone from="2017-10-23 22:00" mzone="Africa_Central"/>
 			</timezone>
 			<timezone type="America/Adak">
@@ -1219,8 +1219,8 @@ For terms of use, see http://www.unicode.org/copyright.html
 				<usesMetazone mzone="Europe_Central"/>
 			</timezone>
 			<timezone type="Europe/Dublin">
-				<usesMetazone mzone="Irish" to="1971-10-31 02:00"/>
-				<usesMetazone mzone="GMT" from="1971-10-31 02:00"/>
+				<usesMetazone mzone="Irish" to="1971-10-31 02:00" stdOffset="+00" dstOffset="+01"/>
+				<usesMetazone mzone="GMT" from="1971-10-31 02:00" stdOffset="+00" dstOffset="+01"/>
 			</timezone>
 			<timezone type="Europe/Gibraltar">
 				<usesMetazone mzone="Europe_Central"/>

docs/ldml/tr35-dates.md

@@ -1511,6 +1511,15 @@ A metazone's display fields become a secondary fallback if an appropriate data f
 
 Note that the dates and times are specified in UTC, not local time.
 
+_usesMetazone_ can also optionally specify which offset is considered standard time, and which offset is considered daylight time. This is required for some zone such as `Europe/Dublin` where TZDB returns inconsistent results depending on platform/build mode etc.:
+
+```xml
+<timezone type="Europe/Dublin">
+    <usesMetazone mzone="Irish" to="1971-10-31 02:00" stdOffset="+00" dstOffset="+01"/>
+    <usesMetazone mzone="GMT" from="1971-10-31 02:00" stdOffset="+00" dstOffset="+01"/>
+</timezone>
+```
+
 The metazones can then have translations in different locale files, such as the following.
 
 ```xml
@@ -1580,6 +1589,8 @@ The `commonlyUsed` element is now deprecated. The CLDR committee has found it ne
 <!ATTLIST usesMetazone mzone NMTOKEN #REQUIRED >
 <!ATTLIST usesMetazone from CDATA #IMPLIED >
 <!ATTLIST usesMetazone to CDATA #IMPLIED >
+<!ATTLIST usesMetazone stdOffset CDATA #IMPLIED >
+<!ATTLIST usesMetazone dstOffset CDATA #IMPLIED >
 
 <!ELEMENT mapTimezones ( mapZone* ) >
 <!ATTLIST mapTimezones type NMTOKEN #IMPLIED >

tools/cldr-code/src/main/resources/org/unicode/cldr/util/data/PathHeader.txt

@@ -479,6 +479,16 @@
 //supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone[@to="%A"]/_mzone			; Supplemental ; Metazone ; $1 ; -∞..$2 ; HIDE
 //supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone/_mzone			; Supplemental ; Metazone ; $1 ; -∞..∞ ; HIDE
 
+//supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone[@from="%A"][@to="%A"]/_stdOffset			; Supplemental ; Metazone ; $1-std-offset ; $2-$3 ; HIDE
+//supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone[@from="%A"]/_stdOffset			; Supplemental ; Metazone ; $1-std-offset ; $2..∞ ; HIDE
+//supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone[@to="%A"]/_stdOffset			; Supplemental ; Metazone ; $1-std-offset ; -∞..$2 ; HIDE
+//supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone/_stdOffset			; Supplemental ; Metazone ; $1-std-offset ; -∞..∞ ; HIDE
+
+//supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone[@from="%A"][@to="%A"]/_dstOffset			; Supplemental ; Metazone ; $1-dst-offset ; $2-$3 ; HIDE
+//supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone[@from="%A"]/_dstOffset			; Supplemental ; Metazone ; $1-dst-offset ; $2..∞ ; HIDE
+//supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone[@to="%A"]/_dstOffset			; Supplemental ; Metazone ; $1-dst-offset ; -∞..$2 ; HIDE
+//supplementalData/metaZones/metazoneInfo/timezone[@type="%A"]/usesMetazone/_dstOffset			; Supplemental ; Metazone ; $1-dst-offset ; -∞..∞ ; HIDE
+
 //supplementalData/metaZones/mapTimezones[@type="%A"]/mapZone[@other="%A"][@territory="%A"]/_type			; Supplemental ; Metazone ; $1 ; $2-$3 ; HIDE
 //supplementalData/metaZones/metazoneIds/metazoneId[@shortId="%A"]/_%E ; Supplemental ; Metazone ; $1 ; $2 ; HIDE
 //supplementalData/primaryZones/primaryZone[@iso3166="%A"]			; Supplemental ; Metazone ; Primary ; $1 ; HIDE