changed to use git history for modified date

Author: AaronJhaj

.github/workflows/java.yaml

@@ -13,7 +13,11 @@ jobs:
     name: Check Copyright
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - name: Checkout repository
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+          
       - name: Check Copyright
         env:
           EXTENSIONS: "*.java"