Hi pdfjs team,

Please find attach a really simple pdf file to reproduce the issue.
[Date.pdf](https://github.com/mozilla/pdf.js/files/8242310/Date.pdf)
This pdf contains 4 date fields, One with a default format (dd/mm/yyyy) and the 3 others with custom formats:

    -  dd
    -  mm
    -  yyyy

The expected behavior is that whenever I fill dd field with 16 for instance, then when i focus out that field the value displayed is 16 but I get 01.

This happens for dd field and mm but it's working fine for dd/mm/yyyy and yyyy fields.

The initial values of the pdf are properly displayed, this happens only if I focus one of those fields.

Thank you for your time

Best regards.

const handlers = [x => x, x => x.toUpperCase(), x => x.toLowerCase()];
    const buf = [];
    let i = 0;
    const ii = cSource.length;
    let currCase = handlers[0];
    let escaped = false;
    for (const command of cFormat) {
      if (escaped) {
        buf.push(command);
        escaped = false;
        continue;
      }
      if (i >= ii) {
        break;
      }
      switch (command) {
        case "?":
          buf.push(currCase(cSource.charAt(i++)));
          break;
        case "X":
          while (i < ii) {
            const char = cSource.charAt(i++);
            if (
              ("a" <= char && char <= "z") ||
              ("A" <= char && char <= "Z") ||
              ("0" <= char && char <= "9")
            ) {