diff --git a/app/models/doi.rb b/app/models/doi.rb
index 5dd0341f3..d6f88cd50 100644
--- a/app/models/doi.rb
+++ b/app/models/doi.rb
@@ -746,7 +746,7 @@ def event=(value)
 
   def check_dates
     Array.wrap(dates).each do |d|
-      errors.add(:dates, "Date #{d["date"]} is not in a supported format.") unless Date.edtf(d["date"]).present?
+      errors.add(:dates, "Date #{d["date"]} is not a valid date in ISO8601 format.") unless Date.edtf(d["date"]).present?
     end
   end
 
diff --git a/spec/models/doi_spec.rb b/spec/models/doi_spec.rb
index 1813c1cc6..e44b688a1 100644
--- a/spec/models/doi_spec.rb
+++ b/spec/models/doi_spec.rb
@@ -258,13 +258,13 @@
     it "invalid" do
       doi.dates = [{ "date" => "08/01/2019" }]
       expect(doi.save).to be false
-      expect(doi.errors.details).to eq(:dates=>[{:error=>"Date 08/01/2019 is not in a supported format."}])
+      expect(doi.errors.details).to eq(:dates=>[{:error=>"Date 08/01/2019 is not a valid date in ISO8601 format."}])
     end
 
     it "invalid datetime" do
       doi.dates = [{ "date" => "2019-08-01 20:28:15" }]
       expect(doi.save).to be false
-      expect(doi.errors.details).to eq(:dates => [{:error=>"Date 2019-08-01 20:28:15 is not in a supported format."}])
+      expect(doi.errors.details).to eq(:dates => [{:error=>"Date 2019-08-01 20:28:15 is not a valid date in ISO8601 format."}])
     end
   end