diff --git a/common/supplemental/supplementalData.xml b/common/supplemental/supplementalData.xml
index 87acfc21970..b0d3ecab75c 100644
--- a/common/supplemental/supplementalData.xml
+++ b/common/supplemental/supplementalData.xml
@@ -4300,6 +4300,7 @@ XXX Code for transations where no currency is involved
           <calendarSystem type="solar" />
           <inheritEras calendar="gregorian" />
           <eras>
+              <!-- Warning: these historical eras are known to use incorrect start dates -->
               <era type="0" start="645-6-19"/>
               <era type="1" start="650-2-15"/>
               <era type="2" start="672-1-1"/>
@@ -4532,11 +4533,12 @@ XXX Code for transations where no currency is involved
               <era type="229" start="1861-2-19"/>
               <era type="230" start="1864-2-20"/>
               <era type="231" start="1865-4-7"/>
-              <era type="232" start="1868-9-8" code="meiji"/>
-              <era type="233" start="1912-7-30" code="taisho"/>
+
+              <era type="232" start="1868-10-23" code="meiji"/>
+              <era type="233" start="1912-07-30" code="taisho"/>
               <era type="234" start="1926-12-25" code="showa"/>
-              <era type="235" start="1989-1-8" code="heisei"/>
-              <era type="236" start="2019-5-1" code="reiwa"/>
+              <era type="235" start="1989-01-08" code="heisei"/>
+              <era type="236" start="2019-05-01" code="reiwa"/>
           </eras>
         </calendar>
         <calendar type="islamic">