问匹配日期的Java正则表达式

EN

        String input = "which matches dates of format 'january 31, 1976', '9/18/2013', "
                + "and '11-20-1988'. This works fine for those formats, but I'm now encountering dates" +
                "in the European '26th May, 2020' format. I tried adding (\\d{1,2})? at the"+
                "beginning of the regex and adding a ? quantifier after the current day matching section of the regex as such";

    String months_t = "(january|february|march|april|may|june|july|august|september|october|november|december)";
    String months_d = "(1[012]|0?[1-9])";
    String days_d = "(3[01]|[12][0-9]|0?[1-9])"; //"\\d{1,2}";
    String year_d = "((19|20)\\d\\d)";
    String days_d_a = "(" + days_d + "(th|rd|nd|st)?)";

    // 'mm/dd/yyyy', and 'mm-dd-yyyy'
    String regexp1 = "(" + months_d + "[/-]" + days_d + "[/-]"
            + year_d + ")";
    // 'Month dd, yyyy', and 'dd Month, yyyy'
    String regexp2 = "(((" + months_t + "\\s*" + days_d_a + ")|("
            + days_d_a + "\\s*" + months_t + "))[,\\s]+" + year_d + ")";
    String regexp = "(?i)" + regexp1 + "|" + regexp2;

    Pattern pMod = Pattern.compile(regexp);
    Matcher mMod = pMod.matcher(input);

    while (mMod.find()) {
        System.out.println(mMod.group(0));
    }

january 31, 1976
9/18/2013
11-20-1988
26th May, 2020