diff --git a/swh/indexer/metadata_dictionary/base.py b/swh/indexer/metadata_dictionary/base.py
--- a/swh/indexer/metadata_dictionary/base.py
+++ b/swh/indexer/metadata_dictionary/base.py
@@ -148,6 +148,10 @@
     """List of fields that are simple strings, and don't need any
     normalization."""
 
+    date_fields: List[str] = []
+    """List of fields that are strings that should be typed as http://schema.org/Date
+    """
+
     uri_fields: List[str] = []
     """List of fields that are simple URIs, and don't need any
     normalization."""
@@ -167,7 +171,7 @@
         simple_terms = {
             str(term)
             for (key, term) in cls.mapping.items()
-            if key in cls.string_fields + cls.uri_fields
+            if key in cls.string_fields + cls.date_fields + cls.uri_fields
             or hasattr(cls, "normalize_" + cls._normalize_method_name(key))
         }
 
@@ -240,6 +244,14 @@
                 elif k in self.string_fields and isinstance(v, list):
                     for item in v:
                         graph.add((root, codemeta_key, rdflib.Literal(item)))
+                elif k in self.date_fields and isinstance(v, str):
+                    typed_v = rdflib.Literal(v, datatype=SCHEMA.Date)
+                    graph.add((root, codemeta_key, typed_v))
+                elif k in self.date_fields and isinstance(v, list):
+                    for item in v:
+                        if isinstance(item, str):
+                            typed_item = rdflib.Literal(item, datatype=SCHEMA.Date)
+                            graph.add((root, codemeta_key, typed_item))
                 elif k in self.uri_fields and isinstance(v, str):
                     # Workaround for https://github.com/digitalbazaar/pyld/issues/91 : drop
                     # URLs that are blatantly invalid early, so PyLD does not crash.
diff --git a/swh/indexer/metadata_dictionary/cff.py b/swh/indexer/metadata_dictionary/cff.py
--- a/swh/indexer/metadata_dictionary/cff.py
+++ b/swh/indexer/metadata_dictionary/cff.py
@@ -25,6 +25,7 @@
     filename = b"CITATION.cff"
     mapping = CROSSWALK_TABLE["Citation File Format Core (CFF-Core) 1.0.2"]
     string_fields = ["keywords", "license", "abstract", "version", "doi"]
+    date_fields = ["date-released"]
     uri_fields = ["repository-code"]
 
     def _translate_author(self, graph: Graph, author: dict) -> rdflib.term.Node:
@@ -57,7 +58,3 @@
     def normalize_license(self, s: str) -> URIRef:
         if isinstance(s, str):
             return SPDX + s
-
-    def normalize_date_released(self, s: str) -> Literal:
-        if isinstance(s, str):
-            return Literal(s, datatype=SCHEMA.Date)
diff --git a/swh/indexer/metadata_dictionary/github.py b/swh/indexer/metadata_dictionary/github.py
--- a/swh/indexer/metadata_dictionary/github.py
+++ b/swh/indexer/metadata_dictionary/github.py
@@ -22,14 +22,18 @@
         **CROSSWALK_TABLE["GitHub"],
         "topics": SCHEMA.keywords,  # TODO: submit this to the official crosswalk
     }
-    string_fields = [
+    uri_fields = [
         "archive_url",
+        "html_url",
+        "issues_url",
+    ]
+    date_fields = [
         "created_at",
         "updated_at",
+    ]
+    string_fields = [
         "description",
         "full_name",
-        "html_url",
-        "issues_url",
         "topics",
     ]
 
diff --git a/swh/indexer/tests/metadata_dictionary/test_github.py b/swh/indexer/tests/metadata_dictionary/test_github.py
--- a/swh/indexer/tests/metadata_dictionary/test_github.py
+++ b/swh/indexer/tests/metadata_dictionary/test_github.py
@@ -32,6 +32,7 @@
     assert {
         "http://schema.org/name",
         "http://schema.org/license",
+        "http://schema.org/dateCreated",
         "https://forgefed.org/ns#forks",
         "https://www.w3.org/ns/activitystreams#totalItems",
     } <= terms
@@ -133,9 +134,9 @@
         "license": "https://spdx.org/licenses/GPL-3.0",
         "name": "SoftwareHeritage/swh-indexer",
         "description": "GitHub mirror of Metadata indexer",
-        "schema:codeRepository": "https://github.com/SoftwareHeritage/swh-indexer",
-        "schema:dateCreated": "2017-01-31T13:05:39Z",
-        "schema:dateModified": "2022-06-22T08:02:20Z",
+        "codeRepository": "https://github.com/SoftwareHeritage/swh-indexer",
+        "dateCreated": "2017-01-31T13:05:39Z",
+        "dateModified": "2022-06-22T08:02:20Z",
     }