lib/timing/time_in_zone.rb in timing-0.0.3 vs lib/timing/time_in_zone.rb in timing-0.0.4

@@ -22,15 +22,18 @@
     alias_method :utc_offset, :zone_offset
     alias_method :gmt_offset, :zone_offset
     alias_method :gmtoff,     :zone_offset
 
     def +(seconds)
+      raise ArgumentError, "#{seconds} must be a valid seconds count" unless seconds.is_a? Numeric
       self.class.new (time + seconds), zone_offset
     end
 
     def -(seconds)
-      self.class.new (time - seconds), zone_offset
+      raise ArgumentError, "#{seconds} must be a time or a valid seconds count" unless seconds.respond_to? :to_f
+      result = self.class.at (time.to_f - seconds.to_f), zone_offset
+      seconds.is_a?(Numeric) ? result : result.to_f
     end
 
     def utc?
       zone_offset == 0
     end
@@ -54,9 +57,21 @@
     end
     alias_method :inspect, :to_s
 
     def strftime(format)
       time_with_offset.strftime format.gsub('%Z', '').gsub('%z', zone_offset.to_s)
+    end
+
+    def iso8601
+      strftime "%FT%T#{zone_offset.iso8601}"
+    end
+
+    def as_json(*args)
+      iso8601
+    end
+
+    def to_json(*args)
+      "\"#{as_json(*args)}\""
     end
 
     %w(hour day week month year).each do |interval|
       beginning_method_name = "beginning_of_#{interval}"
       define_method beginning_method_name do
\ No newline at end of file