Fix Meiji start date (#6432)

Fixes #4892

Author: robertbastian

components/calendar/src/cal/japanese.rs

@@ -494,8 +494,8 @@ impl Date<JapaneseExtended> {
 
 const MEIJI_START: EraStartDate = EraStartDate {
     year: 1868,
-    month: 9,
-    day: 8,
+    month: 10,
+    day: 23,
 };
 const TAISHO_START: EraStartDate = EraStartDate {
     year: 1912,

provider/data/calendar/data/calendar_japanese_extended_v1.rs.data

@@ -1,8 +1,8 @@
 calendar/chinese/v1, <singleton>, 782B, 754B, 134f5ec7c9bdc494
 calendar/dangi/v1, <singleton>, 782B, 754B, 79d5d32449956411
 calendar/hijri/simulated/mecca/v1, <singleton>, 532B, 504B, ad7346b38a43c235
-calendar/japanese/extended/v1, <singleton>, 5238B, 5216B, 781ca7801695fa36
-calendar/japanese/modern/v1, <singleton>, 134B, 111B, b31e52deaf52706f
+calendar/japanese/extended/v1, <singleton>, 5238B, 5216B, e80e648736f019
+calendar/japanese/modern/v1, <singleton>, 134B, 111B, ec96742e22e8fc30
 calendar/week/v1, <lookup>, 292B, 72 identifiers
 calendar/week/v1, <total>, 20B, 20B, 10 unique payloads
 calendar/week/v1, und, 2B, 2B, db63f20c2a6a914a

provider/data/calendar/data/calendar_japanese_modern_v1.rs.data

@@ -285,13 +285,19 @@ fn process_era_dates_map(
                 // https://unicode-org.atlassian.net/browse/CLDR-18388 for why we need to do + 2
                 let idx = (idx.parse::<usize>().unwrap() + 2).to_string();
                 if let Some(start) = era.start.as_mut() {
+                    // All pre-Taisho start dates are known to be wrong, this at least makes them valid.
+                    // See https://unicode-org.atlassian.net/browse/CLDR-11400
                     if start.month == 2 && start.day > 28 {
                         start.day = if calendrical_calculations::iso::is_leap_year(start.year) {
                             29
                         } else {
                             28
                         };
                     }
+                    if era.code.as_deref() == Some("meiji") {
+                        start.month = 10;
+                        start.day = 23;
+                    }
                 }
                 (idx, era)
             })