diff --git a/swh/loader/core/tests/test_utils.py b/swh/loader/core/tests/test_utils.py
--- a/swh/loader/core/tests/test_utils.py
+++ b/swh/loader/core/tests/test_utils.py
@@ -3,6 +3,7 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+from datetime import datetime
 import os
 import signal
 from time import sleep
@@ -15,6 +16,7 @@
     CloneTimeout,
     clean_dangling_folders,
     clone_with_timeout,
+    parse_visit_date,
 )
 
 
@@ -145,3 +147,25 @@
         clone_with_timeout(src, dest, ignores_sigterm, timeout)
     killed = True
     assert e.value.args == (src, timeout, killed)
+
+
+VISIT_DATE_STR = "2021-02-17 15:50:04.518963"
+VISIT_DATE = datetime(2021, 2, 17, 15, 50, 4, 518963)
+
+
+@pytest.mark.parametrize(
+    "input_visit_date,expected_date",
+    [(None, None), (VISIT_DATE, VISIT_DATE), (VISIT_DATE_STR, VISIT_DATE),],
+)
+def test_utils_parse_visit_date(input_visit_date, expected_date):
+    assert parse_visit_date(input_visit_date) == expected_date
+
+
+def test_utils_parse_visit_date_now():
+    actual_date = parse_visit_date("now")
+    assert isinstance(actual_date, datetime)
+
+
+def test_utils_parse_visit_date_fails():
+    with pytest.raises(ValueError, match="invalid"):
+        parse_visit_date(10)  # not a string nor a date
diff --git a/swh/loader/core/utils.py b/swh/loader/core/utils.py
--- a/swh/loader/core/utils.py
+++ b/swh/loader/core/utils.py
@@ -4,15 +4,17 @@
 # See top-level LICENSE file for more information
 
 
+from datetime import datetime, timezone
 import io
 import os
 import shutil
 import signal
 import time
 import traceback
-from typing import Callable
+from typing import Callable, Optional, Union
 
 from billiard import Process, Queue  # type: ignore
+from dateutil.parser import parse
 import psutil
 
 
@@ -103,3 +105,23 @@
 
     if not errors.empty():
         raise CloneFailure(src, dest, errors.get())
+
+
+def parse_visit_date(visit_date: Optional[Union[datetime, str]]) -> Optional[datetime]:
+    """Convert visit date from either None, a string or a datetime to either None or
+       datetime.
+
+    """
+    if visit_date is None:
+        return None
+
+    if isinstance(visit_date, datetime):
+        return visit_date
+
+    if visit_date == "now":
+        return datetime.now(tz=timezone.utc)
+
+    if isinstance(visit_date, str):
+        return parse(visit_date)
+
+    raise ValueError(f"invalid visit date {visit_date!r}")