code: function toTechTimeFormat(
    dt,
    {
      suppressSeconds = false,
      suppressMilliseconds = false,
      includeOffset,
      includeZone = false,
      spaceZone = false
    }
  ) {
    let fmt = "HH:mm";
  
    if (!suppressSeconds || dt.second !== 0 || dt.millisecond !== 0) {
      fmt += ":ss";
      if (!suppressMilliseconds || dt.millisecond !== 0) {
        fmt += ".SSS";
      }
    }
  
    if ((includeZone || includeOffset) && spaceZone) {
      fmt += " ";
    }
  
    if (includeZone) {
      fmt += "z";
    } else if (includeOffset) {
      fmt += "ZZ";
    }
  
    return toTechFormat(dt, fmt);
  }
docs: technical time formats (e.g. the time part of ISO 8601), take some options and this commonizes their handling