lightdm-webkit2-greeter/themes/gruvbox/js/time-date.js

class TimeDate {
  constructor() {
    this._timeLabel = document.querySelector("#time-date #time-label");
    this._dateLabel = document.querySelector("#time-date #date-label");
    this._init();
  }

  _updateTimeDate() {
    let date = theme_utils.get_current_localized_date();
    let time = theme_utils.get_current_localized_time();

    this._dateLabel.innerText = date;
    this._timeLabel.innerText = time;
  }

  _setTimer() {
    this._updateTimeDate();
    setInterval(() => {
      this._updateTimeDate();
    }, 1000);
  }

  _init() {
    this._setTimer();
  }
}