def iso_time_string(val, show_tzinfo=False):
    """
    Takes either a date, datetime or a string, and returns the standard ISO
    formatted string for that date/time, with any fractional second portion
    removed.
    """
    if not val:
        return ""
    if isinstance(val, six.string_types):
        dt = _parse_datetime_string(val)
    else:
        dt = val
    if not isinstance(dt, datetime.datetime):
        dt = datetime.datetime.fromordinal(dt.toordinal())
    has_tz = (dt.tzinfo is not None)
    if show_tzinfo and has_tz:
        # Need to remove the colon in the TZ portion
        ret = "".join(dt.isoformat().rsplit(":", 1))
    elif show_tzinfo and not has_tz:
        ret = "%s+0000" % dt.isoformat().split(".")[0]
    elif not show_tzinfo and has_tz:
        ret = dt.isoformat()[:-6]
    elif not show_tzinfo and not has_tz:
        ret = dt.isoformat().split(".")[0]
    return ret