diff --git a/swh/storage/converters.py b/swh/storage/converters.py
index ca79d020..206e5769 100644
--- a/swh/storage/converters.py
+++ b/swh/storage/converters.py
@@ -1,213 +1,217 @@
 # Copyright (C) 2015  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import datetime
 import numbers
 
 
 DEFAULT_AUTHOR = {
     'name': b'',
     'email': b'',
 }
 
 DEFAULT_DATE = {
     'timestamp': None,
     'offset': 0,
 }
 
 
 def author_to_db(author):
     """Convert a swh-model author to its DB representation.
 
     Args: a swh-model compatible author
     Returns:
         a dict containing two keys: author and email
     """
     if author is None:
         return DEFAULT_AUTHOR
 
     return author
 
 
 def db_to_author(name, email):
     """Convert the DB representation of an author to a swh-model author.
 
     Args:
         name (bytes): the author's name
         email (bytes): the author's email
 
     Returns:
         a dict with two keys: author and email.
     """
 
     return {
         'name': name,
         'email': email,
     }
 
 
 def db_to_date(date, offset):
     """Convert the DB representation of a date to a swh-model compatible date.
 
     Args:
         date (datetime.datetime): a date pulled out of the database
         offset (int): an integer number of minutes representing an UTC offset
 
     Returns:
         a datetime.datetime object, using a timezone with the proper offset.
     """
 
     if date is None:
         return None
 
     new_tz = datetime.timezone(datetime.timedelta(minutes=offset))
     return date.astimezone(tz=new_tz)
 
 
 def date_to_db(date_offset):
     """Convert a swh-model date_offset to its DB representation.
 
     Args: a swh-model compatible date_offset
     Returns:
         a dict containing a numeric timestamp and an integer offset
 
     """
 
     if date_offset is None:
         return DEFAULT_DATE
 
     if isinstance(date_offset, numbers.Real):
         date_offset = datetime.datetime.fromtimestamp(date_offset,
                                                       tz=datetime.timezone.utc)
 
     if isinstance(date_offset, datetime.datetime):
         timestamp = date_offset
         utcoffset = date_offset.utcoffset()
         offset = int(utcoffset.total_seconds()) // 60
     else:
-        timestamp = date_offset['timestamp']
+        if isinstance(date_offset['timestamp'], numbers.Real):
+            timestamp = datetime.datetime.fromtimestamp(
+                date_offset['timestamp'], tz=datetime.timezone.utc)
+        else:
+            timestamp = date_offset['timestamp']
         offset = date_offset['offset']
 
     return {
         'timestamp': timestamp.isoformat(),
         'offset': offset,
     }
 
 
 def revision_to_db(revision):
     """Convert a swh-model revision to its database representation.
     """
 
     author = author_to_db(revision['author'])
     date = date_to_db(revision['date'])
     committer = author_to_db(revision['committer'])
     committer_date = date_to_db(revision['committer_date'])
 
     return {
         'id': revision['id'],
         'author_name': author['name'],
         'author_email': author['email'],
         'date': date['timestamp'],
         'date_offset': date['offset'],
         'committer_name': committer['name'],
         'committer_email': committer['email'],
         'committer_date': committer_date['timestamp'],
         'committer_date_offset': committer_date['offset'],
         'type': revision['type'],
         'directory': revision['directory'],
         'message': revision['message'],
         'metadata': revision['metadata'],
         'synthetic': revision['synthetic'],
         'parents': [
             {
                 'id': revision['id'],
                 'parent_id': parent,
                 'parent_rank': i,
             } for i, parent in enumerate(revision['parents'])
         ],
     }
 
 
 def db_to_revision(db_revision):
     """Convert a database representation of a revision to its swh-model
     representation."""
 
     author = db_to_author(
         db_revision['author_name'],
         db_revision['author_email'],
     )
     date = db_to_date(db_revision['date'], db_revision['date_offset'])
 
     committer = db_to_author(
         db_revision['committer_name'],
         db_revision['committer_email'],
     )
     committer_date = db_to_date(
         db_revision['committer_date'],
         db_revision['committer_date_offset'],
     )
 
     parents = []
     if 'parents' in db_revision:
         for parent in db_revision['parents']:
             if parent:
                 parents.append(parent)
 
     return {
         'id': db_revision['id'],
         'author': author,
         'date': date,
         'committer': committer,
         'committer_date': committer_date,
         'type': db_revision['type'],
         'directory': db_revision['directory'],
         'message': db_revision['message'],
         'metadata': db_revision['metadata'],
         'synthetic': db_revision['synthetic'],
         'parents': parents,
     }
 
 
 def release_to_db(release):
     """Convert a swh-model release to its database representation.
     """
 
     author = author_to_db(release['author'])
     date = date_to_db(release['date'])
 
     return {
         'id': release['id'],
         'author_name': author['name'],
         'author_email': author['email'],
         'date': date['timestamp'],
         'date_offset': date['offset'],
         'name': release['name'],
         'revision': release['target'],
         'comment': release['message'],
         'synthetic': release['synthetic'],
     }
 
 
 def db_to_release(db_release):
     """Convert a database representation of a release to its swh-model
     representation.
     """
 
     author = db_to_author(
         db_release['author_name'],
         db_release['author_email'],
     )
     date = db_to_date(db_release['date'], db_release['date_offset'])
 
     return {
         'author': author,
         'date': date,
         'id': db_release['id'],
         'name': db_release['name'],
         'message': db_release['comment'],
         'synthetic': db_release['synthetic'],
         'target': db_release['revision'],
         'target_type': 'revision',
     }