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diff --git a/spec/ruby/core/time/utc_spec.rb b/spec/ruby/core/time/utc_spec.rb
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+++ b/spec/ruby/core/time/utc_spec.rb
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+require_relative '../../spec_helper'
+require_relative 'shared/gm'
+require_relative 'shared/gmtime'
+require_relative 'shared/time_params'
+
+describe "Time#utc?" do
+  it "returns true only if time represents a time in UTC (GMT)" do
+    Time.now.utc?.should == false
+    Time.now.utc.utc?.should == true
+  end
+
+  it "treats time as UTC what was created in different ways" do
+    Time.now.utc.utc?.should == true
+    Time.now.gmtime.utc?.should == true
+    Time.now.getgm.utc?.should == true
+    Time.now.getutc.utc?.should == true
+    Time.utc(2022).utc?.should == true
+  end
+
+  it "does treat time with 'UTC' offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "UTC").utc?.should == true
+    Time.now.localtime("UTC").utc?.should == true
+    Time.at(Time.now, in: 'UTC').utc?.should == true
+
+    Time.new(2022, 1, 1, 0, 0, 0, in: "UTC").utc?.should == true
+    Time.now(in: "UTC").utc?.should == true
+  end
+
+  it "does treat time with Z offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "Z").utc?.should == true
+    Time.now.localtime("Z").utc?.should == true
+    Time.at(Time.now, in: 'Z').utc?.should == true
+
+    Time.new(2022, 1, 1, 0, 0, 0, in: "Z").utc?.should == true
+    Time.now(in: "Z").utc?.should == true
+  end
+
+  it "does treat time with -00:00 offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "-00:00").utc?.should == true
+    Time.now.localtime("-00:00").utc?.should == true
+    Time.at(Time.now, in: '-00:00').utc?.should == true
+  end
+
+  it "does not treat time with +00:00 offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "+00:00").utc?.should == false
+    Time.now.localtime("+00:00").utc?.should == false
+    Time.at(Time.now, in: "+00:00").utc?.should == false
+  end
+
+  it "does not treat time with 0 offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, 0).utc?.should == false
+    Time.now.localtime(0).utc?.should == false
+    Time.at(Time.now, in: 0).utc?.should == false
+  end
+end
+
+describe "Time.utc" do
+  it_behaves_like :time_gm, :utc
+  it_behaves_like :time_params, :utc
+  it_behaves_like :time_params_10_arg, :utc
+  it_behaves_like :time_params_microseconds, :utc
+end
+
+describe "Time#utc" do
+  it_behaves_like :time_gmtime, :utc
+end