function datetimeToDate(datetime_str, use_utc) {
  // Return a JS Date object from the given python datetime_str string.
  // if the optional boolean use_utc argument is given, the datetime_str
  // will be treated as a UTC datetime_str
  "use strict";
  var datetime_parts = datetime_str.split(" ", 2),
    date_parts = datetime_parts[0].split("-"),
    time_parts = datetime_parts[1].split(":"),
    second_parts = time_parts[2].split('.'),
    mkdate,
    s2i,
    smu2ims;
  use_utc = use_utc === undefined ? false : use_utc;
	
  // The Date constructors don't work with .apply(), so lambdas
  if (use_utc) {
    mkdate = function (y, m, d, hr, min, sec, ms) {
      return new Date(Date.UTC(y, m, d, hr, min, sec, ms));
    };
  } else {
    mkdate = function (y, m, d, hr, min, sec, ms) {
      return new Date(y, m, d, hr, min, sec, ms);
    };
  }
	
  // string to int with radix 10
  s2i = function (i_str) { return parseInt(i_str, 10); };
	
  // string microsecond (aka mu) to int millisecond (aka ms)
  smu2ims = function (f_str) {
    return Math.round(parseFloat(f_str) * 1000);
  };
	
  return mkdate(s2i(date_parts[0]), // year
                s2i(date_parts[1]) - 1, // month 
                s2i(date_parts[2]), // day
                s2i(time_parts[0]), // hour
                s2i(time_parts[1]), // minute
                s2i(second_parts[0]), // second
                smu2ims("." + second_parts[1])); // millisecond
}