RFC 4833               Timezone Options for DHCP              April 2007

4.  The TZ POSIX String

   TZ POSIX string is a string suitable for the TZ variable as specified
   by [1] in Section 8.3, with the exception that a string may not begin
   with a colon (":").  This string is NOT terminated by an ASCII NULL.
   Here is an example:

   EST5EDT4,M3.2.0/02:00,M11.1.0/02:00

   In this case, the string is interpreted as a timezone that is
   normally five hours behind UTC, and four hours behind UTC during DST,
   which runs from the second Sunday in March at 02:00 local time
   through the first Sunday in November at 02:00 local time.  Normally
   the timezone is abbreviated "EST" but during DST it is abbreviated
   "EDT".

   Clients and servers implementing other timezone options MUST support
   this option for basic compatibility.

5.  The TZ Name

   TZ Name is the name of a Zone entry in the database commonly referred
   to as the TZ database.  Specifically, in the database's textual form,
   the string refers to the name field of a zone line.  In order for
   this option to be useful, the client must already have a copy of the
   database.  This string is NOT terminated with an ASCII NULL.

   An example string is Europe/Zurich.

   Clients must already have a copy of the TZ Database for this option
   to be useful.  Configuration of the database is beyond the scope of
   this document.  A client that supports this option SHOULD prefer this
   option to POSIX string if it recognizes the TZ Name that was
   returned.  If it doesn't recognize the TZ Name, the client MUST
   ignore this option.