In GridLAB-D timezones follow the Posix TZ standard. Each timezone is described with a string using the form
STZ[hh[:mm][DTZ][,M#[#].#.#/hh:mm,M#[#].#.#/hh:mm]]
where STZ is the 3-digit standard time zone specification and DTZ is the 3 digit daylight time zone specification, hh:mm describes the offset from GMT with negative for each and positive for west, the first M-spec describes the month, week and weekday on which daylight savings starts, and the second on which it ends.
Because GridLAB-D must run historical simulations, the timezone rules may change from year to year. Consequently, there are different section specify the year in which the timezone specification goes into effect. Each year section is described with the string
[YYYY]
The following timezones are currently supported in tzinfo.txt for the United States:
UTC0 ; Coordinated Universal Time ~ never uses DST GMT0 ; Greenwich Mean Time, no DST EST5 ; Eastern no DST CST6 ; Central no DST MST7 ; Mountain no DST PST8 ; Pacific no DST [1970] ; Rules as of 1967 GMT0GMT,M3.5.0/02:00,M10.5.0/2:00 ; GMT, DST last Sun/Mar to last Sun/Oct EST+5EDT,M4.5.0/02:00,M10.5.0/02:00 ; Eastern, DST last Sun/Apr to last Sun/Oct CST+6CDT,M4.5.0/02:00,M10.5.0/02:00 ; Central, DST last Sun/Apr to last Sun/Oct MST+7MDT,M4.5.0/02:00,M10.5.0/02:00 ; Mountain, DST last Sun/Apr to last Sun/Oct PST+8PDT,M4.5.0/02:00,M10.5.0/02:00 ; Pacific, DST last Sun/Apr to last Sun/Oct [1986] ; Rules as of 1986 EST+5EDT,M4.1.0/02:00,M10.5.0/02:00 ; Eastern, DST first Sun/Apr to last Sun/Oct CST+6CDT,M4.1.0/02:00,M10.5.0/02:00 ; Central, DST first Sun/Apr to last Sun/Oct MST+7MDT,M4.1.0/02:00,M10.5.0/02:00 ; Mountain, DST first Sun/Apr to last Sun/Oct PST+8PDT,M4.1.0/02:00,M10.5.0/02:00 ; Pacific, DST first Sun/Apr to last Sun/Oct [2007] ; Rules as of 2007 EST+5EDT,M3.2.0/02:00,M11.1.0/02:00 ; Eastern, DST second Sun/Mar to first Sun/Nov CST+6CDT,M3.2.0/02:00,M11.1.0/02:00 ; Central, DST second Sun/Mar to first Sun/Nov MST+7MDT,M3.2.0/02:00,M11.1.0/02:00 ; Mountain, DST second Sun/Mar to first Sun/Nov PST+8PDT,M3.2.0/02:00,M11.1.0/02:00 ; Pacific, DST second Sun/Mar to first Sun/Nov