diff --git a/.github/workflows/coverage.yaml b/.github/workflows/coverage.yaml
index 0bbabdd..45d7e0d 100644
--- a/.github/workflows/coverage.yaml
+++ b/.github/workflows/coverage.yaml
@@ -16,7 +16,7 @@ jobs:
         go-version: stable
     - name: Calculate coverage
       run: |
-        go test -v -covermode=count -coverprofile=cover.out.raw -coverpkg=./... ./...
+        go test -v -covermode=atomic -coverprofile=cover.out.raw -coverpkg=./... ./...
         # remove mocks from coverage calculation
         grep -v mock_ cover.out.raw > cover.out
     - name: Generage coverage badge
diff --git a/.gitignore b/.gitignore
index 9b1c8b1..dc0c8d2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /dist
+/cover.out
diff --git a/Makefile b/Makefile
index c5dc744..64d11a6 100644
--- a/Makefile
+++ b/Makefile
@@ -20,3 +20,8 @@ build:
 .PHONY: fuzz
 fuzz: mod-tidy generate
 	go test -fuzz='^Fuzz' -fuzztime=10s -v ./internal/server
+
+.PHONY: cover
+cover: mod-tidy generate
+	go test -v -covermode=atomic -coverprofile=cover.out -coverpkg=./... ./...
+	go tool cover -html=cover.out
diff --git a/README.md b/README.md
index 43d5751..53caa7f 100644
--- a/README.md
+++ b/README.md
@@ -58,7 +58,7 @@ Then push some code to main:
     git checkout --orphan badges
     git rm -rf .
     rm -f .gitignore
-    echo 'This branch exists only to contains the coverage badge in the README on `main`.' > README.md
+    echo 'This branch exists only to store the coverage badge in the README on `main`.' > README.md
     git add README.md
     git commit -m 'chore: initialize the badges branch'
     git push origin badges
@@ -101,7 +101,7 @@ Configure the repository:
 
 1. Go to repository Settings > Rules > Rulesets, and import the `protect-default-branch.json` ruleset.
 
-1. That's it.
+That's it.
 
 ## How to contribute
 
diff --git a/internal/server/serve_test.go b/internal/server/serve_test.go
index 7de175f..0fb934f 100644
--- a/internal/server/serve_test.go
+++ b/internal/server/serve_test.go
@@ -47,6 +47,10 @@ func TestGreet(t *testing.T) {
 			expect:      "time travel detected",
 			expectError: true,
 		},
+		"late birthday": {
+			input:  []string{"Foo", "2000-12-22"},
+			expect: "Hello Foo, happy belated birthday for 355 days ago.",
+		},
 	}
 	for name, tc := range testCases {
 		t.Run(name, func(tt *testing.T) {