# A value object representing a time zone. A time zone is simply a named
# offset (in seconds) from GMT. Note that two time zone objects are only
# equivalent if they have both the same offset, and the same name.
#
# A TimeZone instance may be used to convert a Time value to the corresponding
# time zone.
#
# The class also includes #all, which returns a list of all TimeZone objects.
class TimeZone
include Comparable
attr_reader :name, :utc_offset
# Create a new TimeZone object with the given name and offset. The offset is
# the number of seconds that this time zone is offset from UTC (GMT). Seconds
# were chosen as the offset unit because that is the unit that Ruby uses
# to represent time zone offsets (see Time#utc_offset).
def initialize(name, utc_offset)
@name = name
@utc_offset = utc_offset
end
# Returns the offset of this time zone as a formatted string, of the
# format "+HH:MM". If the offset is zero, this returns the empty
# string. If +colon+ is false, a colon will not be inserted into the
# result.
def formatted_offset( colon=true )
return "" if utc_offset == 0
sign = (utc_offset < 0 ? -1 : 1)
hours = utc_offset.abs / 3600
minutes = (utc_offset.abs % 3600) / 60
"%+03d%s%02d" % [ hours * sign, colon ? ":" : "", minutes ]
end
# Compute and return the current time, in the time zone represented by
# +self+.
def now
adjust(Time.now)
end
# Return the current date in this time zone.
def today
now.to_date
end
# Adjust the given time to the time zone represented by +self+.
def adjust(time)
time = time.to_time
time + utc_offset - time.utc_offset
end
# Reinterprets the given time value as a time in the current time
# zone, and then adjusts it to return the corresponding time in the
# local time zone.
def unadjust(time)
time = Time.local(*time.to_time.to_a)
time - utc_offset + time.utc_offset
end
# Compare this time zone to the parameter. The two are comapred first on
# their offsets, and then by name.
def <=>(zone)
result = (utc_offset <=> zone.utc_offset)
result = (name <=> zone.name) if result == 0
result
end
# Returns a textual representation of this time zone.
def to_s
"(GMT#{formatted_offset}) #{name}"
end
@@zones = nil
class << self
# Create a new TimeZone instance with the given name and offset.
def create(name, offset)
zone = allocate
zone.send!(:initialize, name, offset)
zone
end
# Return a TimeZone instance with the given name, or +nil+ if no
# such TimeZone instance exists. (This exists to support the use of
# this class with the #composed_of macro.)
def new(name)
self[name]
end
# Return an array of all TimeZone objects. There are multiple TimeZone
# objects per time zone, in many cases, to make it easier for users to
# find their own time zone.
def all
unless @@zones
@@zones = []
[[-43_200, "International Date Line West" ],
[-39_600, "Midway Island", "Samoa" ],
[-36_000, "Hawaii" ],
[-32_400, "Alaska" ],
[-28_800, "Pacific Time (US & Canada)", "Tijuana" ],
[-25_200, "Mountain Time (US & Canada)", "Chihuahua", "Mazatlan",
"Arizona" ],
[-21_600, "Central Time (US & Canada)", "Saskatchewan", "Guadalajara",
"Mexico City", "Monterrey", "Central America" ],
[-18_000, "Eastern Time (US & Canada)", "Indiana (East)", "Bogota",
"Lima", "Quito" ],
[-14_400, "Atlantic Time (Canada)", "Caracas", "La Paz", "Santiago" ],
[-12_600, "Newfoundland" ],
[-10_800, "Brasilia", "Buenos Aires", "Georgetown", "Greenland" ],
[ -7_200, "Mid-Atlantic" ],
[ -3_600, "Azores", "Cape Verde Is." ],
[ 0, "Dublin", "Edinburgh", "Lisbon", "London", "Casablanca",
"Monrovia" ],
[ 3_600, "Belgrade", "Bratislava", "Budapest", "Ljubljana", "Prague",
"Sarajevo", "Skopje", "Warsaw", "Zagreb", "Brussels",
"Copenhagen", "Madrid", "Paris", "Amsterdam", "Berlin",
"Bern", "Rome", "Stockholm", "Vienna",
"West Central Africa" ],
[ 7_200, "Bucharest", "Cairo", "Helsinki", "Kyev", "Riga", "Sofia",
"Tallinn", "Vilnius", "Athens", "Istanbul", "Minsk",
"Jerusalem", "Harare", "Pretoria" ],
[ 10_800, "Moscow", "St. Petersburg", "Volgograd", "Kuwait", "Riyadh",
"Nairobi", "Baghdad" ],
[ 12_600, "Tehran" ],
[ 14_400, "Abu Dhabi", "Muscat", "Baku", "Tbilisi", "Yerevan" ],
[ 16_200, "Kabul" ],
[ 18_000, "Ekaterinburg", "Islamabad", "Karachi", "Tashkent" ],
[ 19_800, "Chennai", "Kolkata", "Mumbai", "New Delhi" ],
[ 20_700, "Kathmandu" ],
[ 21_600, "Astana", "Dhaka", "Sri Jayawardenepura", "Almaty",
"Novosibirsk" ],
[ 23_400, "Rangoon" ],
[ 25_200, "Bangkok", "Hanoi", "Jakarta", "Krasnoyarsk" ],
[ 28_800, "Beijing", "Chongqing", "Hong Kong", "Urumqi",
"Kuala Lumpur", "Singapore", "Taipei", "Perth", "Irkutsk",
"Ulaan Bataar" ],
[ 32_400, "Seoul", "Osaka", "Sapporo", "Tokyo", "Yakutsk" ],
[ 34_200, "Darwin", "Adelaide" ],
[ 36_000, "Canberra", "Melbourne", "Sydney", "Brisbane", "Hobart",
"Vladivostok", "Guam", "Port Moresby" ],
[ 39_600, "Magadan", "Solomon Is.", "New Caledonia" ],
[ 43_200, "Fiji", "Kamchatka", "Marshall Is.", "Auckland",
"Wellington" ],
[ 46_800, "Nuku'alofa" ]].
each do |offset, *places|
places.each { |place| @@zones << create(place, offset).freeze }
end
@@zones.sort!
end
@@zones
end
# Locate a specific time zone object. If the argument is a string, it
# is interpreted to mean the name of the timezone to locate. If it is a
# numeric value it is either the hour offset, or the second offset, of the
# timezone to find. (The first one with that offset will be returned.)
# Returns +nil+ if no such time zone is known to the system.
def [](arg)
case arg
when String
all.find { |z| z.name == arg }
when Numeric
arg *= 3600 if arg.abs <= 13
all.find { |z| z.utc_offset == arg.to_i }
else
raise ArgumentError, "invalid argument to TimeZone[]: #{arg.inspect}"
end
end
# A regular expression that matches the names of all time zones in
# the USA.
US_ZONES = /US|Arizona|Indiana|Hawaii|Alaska/ unless defined?(US_ZONES)
# A convenience method for returning a collection of TimeZone objects
# for time zones in the USA.
def us_zones
all.find_all { |z| z.name =~ US_ZONES }
end
end
end
