diff --git a/src/lang/japanese.txt b/src/lang/japanese.txt
--- a/src/lang/japanese.txt
+++ b/src/lang/japanese.txt
@@ -5510,10 +5510,10 @@ STR_VEHICLE_NAME_AIRCRAFT_POWERNAUT_HELICOPTER                  :パワーノート社 ヘリコプター
 
 ##id 0x8800
 # Formatting of some strings
-STR_FORMAT_DATE_TINY                                            :{2:NUM}-{1:STRING}-{0:STRING}
+STR_FORMAT_DATE_TINY                                            :{2:NUM}-{1:ZEROFILL_NUM}-{0:ZEROFILL_NUM}
 STR_FORMAT_DATE_SHORT                                           :{1:NUM}年{0:STRING}月
 STR_FORMAT_DATE_LONG                                            :{2:NUM}年{1:STRING}月{0:STRING}日
-STR_FORMAT_DATE_ISO                                             :{2:NUM}-{1:STRING}-{0:STRING}
+STR_FORMAT_DATE_ISO                                             :{2:NUM}-{1:ZEROFILL_NUM}-{0:ZEROFILL_NUM}
 
 STR_FORMAT_COMPANY_NUM                                          :(会社{COMMA})
 STR_FORMAT_GROUP_NAME                                           :グループ {COMMA}