This is used with combinatin of yeeAddons date, prepare teh dd/mm/yyyy input visually but passed "yyyy-mm-dd" on submit to Hubspot in this case. Accepts Keydown (enter) and leaves it be meaning allows it.

elementor-flatpickr-custom-date-input.js

jQuery(document).ready(function ($) {
  /* ------------------------------------------------------------------
   * 1.  Flatpickr options
   * ------------------------------------------------------------------ */
  const flatpickrOptions = {
    // Format that will be written to the hidden input (HubSpot)
    dateFormat: "Y-m-d",

    // Format that the user sees / types
    altFormat: "d/m/Y",

    mode: "single",
    allowInput: true,   // let the user type
    altInput: true,     // create a visible altInput

    // Minimum date that the picker will allow
    minDate: "1900-01-01",
    maxDate: "",

    /* ------------------------------------------------------------------
     * 2.  Detect manual typing
     * ------------------------------------------------------------------ */
    // When the user presses a key in the visible input, set a flag
    onKeyDown: function (e) {
      //e.target === this.input //(the visible altInput)
      this.isTyping = true;
    },

    /* ------------------------------------------------------------------
     * 3.  Handle changes – differentiate between typing & calendar
     * ------------------------------------------------------------------ */
    onChange: function (selectedDates, dateStr, instance) {
      // `dateStr` is the string typed by the user (if any)
      // `selectedDates[0]` is a Date object (if a date was chosen)

      if (instance.isTyping) {
        /* ---- Manual input ---- */
        // Validate the format strictly (dd/mm/yyyy)
        const m = moment(dateStr, "DD/MM/YYYY", true); // true = strict

        if (!m.isValid()) {
          // Show an error and clear the visible field
          console.log("Invalid date format. Please use dd/mm/yyyy");
          // Clear the visible input – use the public API
        //  instance.setDate(null, false); // clears the visible field
          // The hidden field stays unchanged
        } else {
          // Valid manual input – you can run any custom logic here
          console.log("User typed a valid date:", m.format("YYYY-MM-DD"));
          // The hidden field will automatically be updated to YYYY-MM-DD
        }
      } else {
        /* ---- Calendar selection ---- */
        // `selectedDates[0]` is a Date object
        console.log("User selected via calendar:", selectedDates[0].toISOString().slice(0, 10));
        // The hidden field will automatically be updated to YYYY-MM-DD
      }

      // Reset the flag – next change will be considered a new action
      instance.isTyping = false;
    },

    /* ------------------------------------------------------------------
     * 4.  Clean up after the picker closes
     * ------------------------------------------------------------------ */
    onClose: function () {
      this.isTyping = false;
    }
  };

  /* ------------------------------------------------------------------
   * 5.  Initialise Flatpickr on the hidden input
   * ------------------------------------------------------------------ */
  setTimeout(function () {
    // The hidden input that holds the Y‑m‑d value
    const $hiddenInput = $("#form-field-date_of_birth__date_");

    if ($hiddenInput.length) {
      // Initialise Flatpickr on the hidden input
      flatpickr($hiddenInput[0], flatpickrOptions);

      /* ------------------------------------------------------------------
       * 6.  Hide Elementor's pre‑existing visible input
       * ------------------------------------------------------------------ */
      // Elementor often creates a visible <input type="text"> right after the hidden one.
      // We find that sibling and hide it so the user only sees the Flatpickr altInput.
      const $elemVisible = $hiddenInput
        .nextAll('input[type="text"].elementor-date-field')
        .first();

      if ($elemVisible.length) {
      //  $elemVisible.hide();          // hide the Elementor field
        $elemVisible.removeAttr("required"); // optional – let Flatpickr handle validation
      }
    }
  }, 1000); // 1‑second delay – adjust if Elementor needs more time
});