function check_date( msg ) {
    var search = document.search;
    if( search == null ) {
        return;
    }
    var dt = search.dt_ba;
    if( dt == null || ! dt.checked ) {
        return;
    }
    var aday = search.ady.value;
    var bday = search.bdy.value;
    var amo = search.amo.value;
    var bmo = search.bmo.value;
    var ayr = search.ayr.value;
    var byr = search.byr.value;
    if (isNaN(aday) || isNaN(bday) || isNaN(amo) || isNaN(bmo) || isNaN(ayr) || isNaN(byr) ) {
        alert( msg );
        return false;  }
    if (aday < 1 || bday < 1 || amo > 12 || bmo > 12 || amo < 1 || bmo < 1 || ayr < 1971 || byr < 1971 || ayr > 2036 || byr > 2036 ) {
        alert( msg );
        return false;
    }
    mla = new Array(0,31,28,31,30,31,30,31,31,30,31,30,31);
    if ((ayr%4) == 0 ) {
        mla[2] = 29;
    }
    if (aday > mla[amo]) {
        alert( msg );
        return false;
    }
    if ((byr%4) == 0 ) {
        mla[2] = 29;
    } else {
        mla[2] = 28;
    }
    if (bday > mla[bmo]) {
        alert( msg );
        return false;
    }
    return true;
}