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.

buf.push(currCase(char));
              break;
            }
          }
          break;
        case "A":
          while (i < ii) {
            const char = cSource.charAt(i++);
            if (("a" <= char && char <= "z") || ("A" <= char && char <= "Z")) {
              buf.push(currCase(char));
              break;
            }
          }
          break;
        case "9":
          while (i < ii) {
            const char = cSource.charAt(i++);
            if ("0" <= char && char <= "9") {
              buf.push(char);
              break;
            }
          }
          break;
        case "*":
          while (i < ii) {
            buf.push(currCase(cSource.charAt(i++)));
          }
          break;
        case "\\":
          escaped = true;