Function dateString_

* Convert a JS date (millis since epoch) to a formatted string. * @param {number} time The JavaScript time value (ms since epoch) * @param {boolean} utc Wether output UTC or local time * @return {string} A date of one of these forms: * "YYYY/MM/DD", "YYYY/MM/DD HH:MM" or "YYYY/MM/DD HH:MM:SS

(time, utc)