Steps to Reproduce

run fiddle
http://zkfiddle.org/sample/1iabu9j/4-ZK-datefmt-parse-1900

Current Result

date set as 2030 parses as 1930
date set as 2029 parses as 2029

Expected feature Result

Datebox should have an option to choose if dates formated with yy should parse to 19yy or 20yy (or a combination with a switch date between 19yy and 20yy)

Debug Info

https://github.com/zkoss/zk/blob/master/zul/src/archive/web/js/zul/db/datefmt.js#L239-L242