Steps to Reproduce

1. run the attached zul with JDK 9 or 11 and -Djava.locale.providers=JRE,CLDR
2. change the locale to ee

Current Result

WARNING: Invalid format: "mm d lia, yyyy"
java.lang.IllegalArgumentException: Illegal pattern character 'l'
at java.base/java.text.SimpleDateFormat.compile(SimpleDateFormat.java:845)
at java.base/java.text.SimpleDateFormat.initialize(SimpleDateFormat.java:653)
at java.base/java.text.SimpleDateFormat.<init>(SimpleDateFormat.java:624)
at org.zkoss.poi.ss.format.CellDateFormatter.<init>(CellDateFormatter.java:183)
at org.zkoss.poi.ss.format.CellFormatType$3.formatter(CellFormatType.java:53)
at org.zkoss.poi.ss.format.CellFormatPart.getFormatter(CellFormatPart.java:381)
at org.zkoss.poi.ss.format.CellFormatPart.<init>(CellFormatPart.java:206)
at org.zkoss.poi.ss.format.CellFormat.<init>(CellFormat.java:196)
at org.zkoss.poi.ss.format.CellFormat.getInstance(CellFormat.java:172)
at io.keikai.model.impl.sys.FormatEngineImpl.getCellFormat(FormatEngineImpl.java:79)
at io.keikaiex.model.sys.FormatEngineEx.getCellFormat(FormatEngineEx.java:46)
at io.keikai.model.impl.sys.FormatEngineImpl.format0(FormatEngineImpl.java:98)
at io.keikai.model.impl.sys.FormatEngineImpl.format(FormatEngineImpl.java:70)
at io.keikai.ui.impl.CellFormatHelper.getFormatResult(CellFormatHelper.java:1020)
at io.keikai.ui.SpreadsheetCtrlImpl.getCellAttr(SpreadsheetCtrlImpl.java:543)
at io.keikai.ui.SpreadsheetCtrlImpl.getRangeAttrs(SpreadsheetCtrlImpl.java:390)
at io.keikai.ui.Spreadsheet.createActiveRange(Spreadsheet.java:2039)
at io.keikai.ui.Spreadsheet.renderProperties(Spreadsheet.java:1979)

Expected Result

no error

Debug Information