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 actions = {
      AVG: args => args.reduce((acc, value) => acc + value, 0) / args.length,
      SUM: args => args.reduce((acc, value) => acc + value, 0),
      PRD: args => args.reduce((acc, value) => acc * value, 1),
      MIN: args =>
        args.reduce((acc, value) => Math.min(acc, value), Number.MAX_VALUE),
      MAX: args =>
        args.reduce((acc, value) => Math.max(acc, value), Number.MIN_VALUE),
    };
    if (!(cFunction in actions)) {
      throw new TypeError("Invalid function in AFSimple_Calculate");
    }
    const event = globalThis.event;
    const values = [];
    for (const cField of cFields) {
      const field = this._document.getField(cField);
      const number = this.AFMakeNumber(field.value);
      if (number !== null) {
        values.push(number);
      }
    }
    if (values.length === 0) {
      event.value = cFunction === "PRD" ? 1 : 0;
      return;
    }
    const res = actions[cFunction](values);
    event.value = Math.round(1e6 * res) / 1e6;
  }
  AFSpecial_Format(psf) {