TIMEZONES Reference
The clock subsystem is generally configured using the
DATE command. JANOS
defines a set of Timezones for use in displaying local time. These timezones
may or may not utilize Daylight Saving Time (DST). The DATE -T command
displays the current set of available timezones.
The rules for DST may change from time to time as governments alter their
policies. The default list of timezones will likely become incorrect at some
point. JANOS provides a means by which you may define a custom timezone with
or without a DST rule. You may even correct an existing timezone.
DESCRIPTION
The following key format is used to create a new timezone or overwrite an
existing timezone. Note that timezones are identified by their standard
abbreviation (ABBSTD). The timezone for Eastern Standard Time is identified
as "EST". Since the default definition of this timezone includes a Daylight
Saving Time (DST) rule, the DATE command can also select this timezone using
the DST abbreviation "EDT".
reg Timezones/NAME = OFFSET, DESC, ABBSTD [, ABBDST, STMON, STDAY,
STDOW, STTIME, ENDMON, ENDDAY, ENDDOW, ENDTIME, DSTOFS]
NAME
The NAME portion of the key is arbitrary and serves only to differentiate
the key from others.
OFFSET
The offset in minutes from UTC specified in military time in the format
HHMM. For example -0500 subtracts 5 hours from UTC. The value 0630 adds
six and a half hours to UTC.
DESC
Supplies a textual description of the timezone. For instance "Universal
Coordinated" for UTC.
ABBSTD
Defines the standard abbreviation for the timezone. This is the
identifier that is used with the date and time to specify the current
timezone. It is used by the DATE command in setting the current timezone.
If this matches an existing timezone the built-in definition will be
overwritten. Otherwise a new timezone will be created.
The following parameters are required only when specifying a DST rule.
ABBDST
Defines an alternate abbreviation for the timezone. This is the
identifier that is used with the date and time to specify the current
timezone when Daylight Saving Time is in effect. It can be used by the
DATE command in setting the current timezone.
STMON
Specifies the starting month for DST. A 3-character abbreviation is
used: JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, or DEC.
This field is not case-sensitive although uppercase is recommended by
convention.
STDAY
Specifies the starting day of the month. This is a numeric value where
1 specifies the first day of the month. If it is necessary to specify a
certain number of days before the end of the month, a negative value
can be entered. Since DST usually begins (and ends) on a specific day
of the week, this value is used to select the correct part of the month
for that day.
STDOW
Specifies the day of the week on which DST starts. A 3-character
abbreviation is used: SUN, MON, TUE, WED, THU, FRI, or SAT. This field
is not case-sensitive although uppercase is recommended by convention.
This defines the day of the week on or after the starting day. If it is
necessary to specify the day of the week on or before the starting day,
a negative sign may be prepended to the string (e.g. "-SUN").
STTIME
Specifies the starting time for DST in military time using the format
HHMM. For example 0200 indicates 2 o'clock in the morning. This is the
point in time when the clocks are to be adjusted.
ENDMON
Specifies the ending month for DST. A 3-character abbreviation is used:
JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, or DEC. This
field is not case-sensitive although uppercase is recommended by
convention.
ENDDAY
Specifies the ending day of the month. This is a numeric value where 1
specifies the first day of the month. If it is necessary to specify a
certain number of days before the end of the month, a negative value
can be supplied.
ENDDOW
Specifies the day of the week on which DST ends. A 3-character
abbreviation is used: SUN, MON, TUE, WED, THU, FRI, or SAT. This field
is not case-sensitive although uppercase is recommended by convention.
This is the day of the week on or after the ending day. If it is
necessary to specify the day of the week on or before the ending day,
a negative sign may be prepended to the string (e.g. "-SUN").
ENDTIME
Specifies the ending time for DST in military time in the format HHMM.
For example 0200 indicates 2 o'clock in the morning. This is the point
in time when the clocks are to be returned to standard time.
DSTOFS
This defines in minutes the adjustment that occurs when daylight saving
time is in effect. Typically this value is 60 indicating that the clocks
move ahead an hour for DST.
NOTES
There are two forms to the key. The simple form requires only the first 3
fields. This defines a timezone that does not use DST. The full format
requires 13 fields where the additional entries outline the use of DST in
that timezone. The DST definition provides an additional abbreviation,
specifies start and end timing, and defines the time offset.
This Registry key is interpreted, and therefore take effect, on boot. The
new or modified timezones will appear in the table produced by the DATE -T
command. The JNIOR may then be switched to the new timezone which will
remain in existence until the Registry key is removed or altered. Note that
when time is reported to external systems, a custom timezone may not be
recognized if its abbreviation is not common and known to the rest of the
world.
A Timezone key will be ignored if it contains a syntax or value error.
These errors will be reported to the system log (SYSLOG).
EXAMPLES
For example, the following Registry command makes an entry that redefines
the Eastern Timezone in the United States with an ego-centric description
for those of us in Pittsburgh Pennsylvania.
reg Timezones/YinzerTime = "-0500, America/Pittsburgh, EST"
This would not be exactly correct as the EST timezone observes Daylight
Saving Time. We need to also include the rule.
reg Timezones/YinzerTime = "-0500, America/Pittsburgh, EST, EDT,
MAR, 8, SUN, 200, NOV, 1, SUN, 200, 60"
And perhaps instead of redefining EST we would prefer to create our own
timezone, the entry would change as follows. Note that only the ABBSTD
need be changed but we alter the ABBDST to be consistent.
reg Timezones/YinzerTime = "-0500, America/Pittsburgh, YST, YDT,
MAR, 8, SUN, 200, NOV, 1, SUN, 200, 60"
SEE ALSO
HELP Topics:
DATE
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