1 files changed, 11 insertions, 1 deletions
diff --git a/spec/ruby/library/datetime/subtract_spec.rb b/spec/ruby/library/datetime/subtract_spec.rb
index ed88533246..ba01f4eff6 100644
--- a/spec/ruby/library/datetime/subtract_spec.rb
+++ b/spec/ruby/library/datetime/subtract_spec.rb
@@ -4,6 +4,16 @@ require 'date'
 describe "DateTime#-" do
   it "is able to subtract sub-millisecond precision values" do
     date = DateTime.new(2017)
-    ((date + 0.00001) - date).should == Rational(1, 100000)
+    diff = Rational(123456789, 24*60*60*1000*1000)
+    ((date + diff) - date).should == diff
+    (date - (date + diff)).should == -diff
+    (date - (date - diff)).should == diff
+    ((date - diff) - date).should == -diff
+  end
+
+  it "correctly calculates sub-millisecond time differences" do  #5493
+    dt1 = DateTime.new(2018, 1, 1, 0, 0, 30)
+    dt2 = DateTime.new(2018, 1, 1, 0, 1, 29.000001)
+    ((dt2 - dt1) * 24 * 60 * 60).should == 59.000001
   end
 end