/**
 * Formats an input date to w3c standard date format
 * @param date {number|string} Optional if not defined current date is returned
 *
 * @returns {string} date in a standard format as a string
 */
export const w3cDate = (date?: number | string): string => {
  let result = new Date()
  if (typeof date === 'number' || typeof date === 'string') {
    result = new Date(date)
  }
  const str = result.toISOString()
  return str.substr(0, str.length - 5) + 'Z'
}