js验证日期时间格式正则表达式

var _reTimeReg = /^(?:19|20)[0-9][0-9]-(?:(?:0[1-9])|(?:1[0-2]))-(?:(?:[0-2][1-9])|(?:[1-3][0-1])) (?:(?:[0-2][0-3])|(?:[0-1][0-9])):[0-5][0-9]:[0-5][0-9]$/;
var jhsjq=$("#jhsjq").val();

if(!_reTimeReg.test(jhsjq)){

alert("开始时间格式应为yyyy-MM-dd HH:mm:ss");
$("#jhsjq").focus();
return false;
}