Validando datas em pt-br com jQuery Validate
Assim:
$.validator.addMethod( "date", function(value, element) { var check = false; var re = /^\d{1,2}\/\d{1,2}\/\d{4}$/; if( re.test(value)){ var adata = value.split('/'); var gg = parseInt(adata[0],10); var mm = parseInt(adata[1],10); var aaaa = parseInt(adata[2],10); var xdata = new Date(aaaa,mm-1,gg); if ( ( xdata.getFullYear() == aaaa ) && ( xdata.getMonth () == mm - 1 ) && ( xdata.getDate() == gg ) ) check = true; else check = false; } else check = false; return this.optional(element) || check; }, "Insira uma data válida" );