:00 EST (-0500)'
    >>> eastern.normalize(loc_dt - timedelta(minutes=10)).strftime(fmt)
    '2002-10-27 01:50:00 EDT (-0400)'
    >>> (loc_dt + timedelta(minutes=10)).strftime(fmt)
    '2002-10-27 01:10:00 EST (-0500)'

    Raises UnknownTimeZoneError if passed an unknown zone.

    >>> try:
    ...     timezone('Asia/Shangri-La')
    ... except UnknownTimeZoneError:
    ...     print('Unknown')
    Unknown

    >>> try:
    ...     timezone(unicode('\N{TRADE MARK SIGN}'))
    ... except UnknownTimeZoneError:
    ...     print('Unknown')
    Unknown

    NÚ