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@@ -325,6 +325,9 @@
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     ZONES.sort!
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     ZONES.freeze
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     ZONES_MAP.freeze
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+
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+    US_ZONES = ZONES.find_all { |z| z.name =~ /US|Arizona|Indiana|Hawaii|Alaska/ }
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+    US_ZONES.freeze
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   end
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   class << self
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@@ -361,14 +364,10 @@
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       end
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     end
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-    # A regular expression that matches the names of all time zones in
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-    # the USA.
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-    US_ZONES = /US|Arizona|Indiana|Hawaii|Alaska/.freeze
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-
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     # A convenience method for returning a collection of TimeZone objects
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     # for time zones in the USA.
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     def us_zones
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-      all.find_all { |z| z.name =~ US_ZONES }
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+      US_ZONES
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     end
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   end
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 end