diff --git a/src/borg/archiver.py b/src/borg/archiver.py
index ea70f412a..eac059bb7 100644
--- a/src/borg/archiver.py
+++ b/src/borg/archiver.py
@@ -360,6 +360,10 @@ class Archiver:
                 if chunks_healthy is not None:
                     item._dict['chunks_healthy'] = chunks
                 item._dict.pop('source')  # not used for hardlinks any more, replaced by hlid
+            for attr in 'atime', 'ctime', 'mtime', 'birthtime':
+                if attr in item:
+                    ns = getattr(item, attr)  # decode (bigint or Timestamp) --> int ns
+                    setattr(item, attr, ns)  # encode int ns --> msgpack.Timestamp only, no bigint any more
             item._dict.pop('hardlink_master', None)  # not used for hardlinks any more, replaced by hlid
             item._dict.pop('acl', None)  # remove remnants of bug in attic <= 0.13
             item.get_size(memorize=True)  # if not already present: compute+remember size for items with chunks
diff --git a/src/borg/cache.py b/src/borg/cache.py
index 6fa74e692..6cd612359 100644
--- a/src/borg/cache.py
+++ b/src/borg/cache.py
@@ -19,7 +19,7 @@ from .helpers import Location
 from .helpers import Error
 from .helpers import Manifest
 from .helpers import get_cache_dir, get_security_dir
-from .helpers import int_to_bigint, bigint_to_int, bin_to_hex, parse_stringified_list
+from .helpers import bin_to_hex, parse_stringified_list
 from .helpers import format_file_size
 from .helpers import safe_ns
 from .helpers import yes
@@ -28,6 +28,7 @@ from .helpers import ProgressIndicatorPercent, ProgressIndicatorMessage
 from .helpers import set_ec, EXIT_WARNING
 from .helpers import safe_unlink
 from .helpers import msgpack
+from .helpers.msgpack import int_to_timestamp, timestamp_to_int
 from .item import ArchiveItem, ChunkListEntry
 from .crypto.key import PlaintextKey
 from .crypto.file_integrity import IntegrityCheckedFile, DetachedIntegrityCheckedFile, FileIntegrityError
@@ -623,7 +624,7 @@ class LocalCache(CacheStatsMixin):
                     # this is to avoid issues with filesystem snapshots and cmtime granularity.
                     # Also keep files from older backups that have not reached BORG_FILES_CACHE_TTL yet.
                     entry = FileCacheEntry(*msgpack.unpackb(item))
-                    if entry.age == 0 and bigint_to_int(entry.cmtime) < self._newest_cmtime or \
+                    if entry.age == 0 and timestamp_to_int(entry.cmtime) < self._newest_cmtime or \
                        entry.age > 0 and entry.age < ttl:
                         msgpack.pack((path_hash, entry), fd)
                         entry_count += 1
@@ -1018,10 +1019,10 @@ class LocalCache(CacheStatsMixin):
         if 'i' in cache_mode and entry.inode != st.st_ino:
             files_cache_logger.debug('KNOWN-CHANGED: file inode number has changed: %r', hashed_path)
             return True, None
-        if 'c' in cache_mode and bigint_to_int(entry.cmtime) != st.st_ctime_ns:
+        if 'c' in cache_mode and timestamp_to_int(entry.cmtime) != st.st_ctime_ns:
             files_cache_logger.debug('KNOWN-CHANGED: file ctime has changed: %r', hashed_path)
             return True, None
-        elif 'm' in cache_mode and bigint_to_int(entry.cmtime) != st.st_mtime_ns:
+        elif 'm' in cache_mode and timestamp_to_int(entry.cmtime) != st.st_mtime_ns:
             files_cache_logger.debug('KNOWN-CHANGED: file mtime has changed: %r', hashed_path)
             return True, None
         # we ignored the inode number in the comparison above or it is still same.
@@ -1049,7 +1050,7 @@ class LocalCache(CacheStatsMixin):
         elif 'm' in cache_mode:
             cmtime_type = 'mtime'
             cmtime_ns = safe_ns(st.st_mtime_ns)
-        entry = FileCacheEntry(age=0, inode=st.st_ino, size=st.st_size, cmtime=int_to_bigint(cmtime_ns), chunk_ids=ids)
+        entry = FileCacheEntry(age=0, inode=st.st_ino, size=st.st_size, cmtime=int_to_timestamp(cmtime_ns), chunk_ids=ids)
         self.files[path_hash] = msgpack.packb(entry)
         self._newest_cmtime = max(self._newest_cmtime or 0, cmtime_ns)
         files_cache_logger.debug('FILES-CACHE-UPDATE: put %r [has %s] <- %r',
diff --git a/src/borg/helpers/msgpack.py b/src/borg/helpers/msgpack.py
index 2ace88fee..411f00fec 100644
--- a/src/borg/helpers/msgpack.py
+++ b/src/borg/helpers/msgpack.py
@@ -24,7 +24,7 @@ from msgpack import unpackb as mp_unpackb
 from msgpack import unpack as mp_unpack
 from msgpack import version as mp_version
 
-from msgpack import ExtType
+from msgpack import ExtType, Timestamp
 from msgpack import OutOfData
 
 
@@ -164,7 +164,7 @@ def get_limited_unpacker(kind):
     return Unpacker(**args)
 
 
-def bigint_to_int(mtime):
+def bigint_to_int(mtime):  # legacy
     """Convert bytearray to int
     """
     if isinstance(mtime, bytes):
@@ -172,7 +172,7 @@ def bigint_to_int(mtime):
     return mtime
 
 
-def int_to_bigint(value):
+def int_to_bigint(value):  # legacy
     """Convert integers larger than 64 bits to bytearray
 
     Smaller integers are left alone
@@ -180,3 +180,14 @@ def int_to_bigint(value):
     if value.bit_length() > 63:
         return value.to_bytes((value.bit_length() + 9) // 8, 'little', signed=True)
     return value
+
+
+def int_to_timestamp(ns):
+    return Timestamp.from_unix_nano(ns)
+
+
+def timestamp_to_int(ts):
+    if isinstance(ts, Timestamp):
+        return ts.to_unix_nano()
+    # legacy support note: we need to keep the bigint conversion for compatibility with borg < 1.3 archives.
+    return bigint_to_int(ts)
diff --git a/src/borg/helpers/parseformat.py b/src/borg/helpers/parseformat.py
index 3e145ada2..9bcbce22c 100644
--- a/src/borg/helpers/parseformat.py
+++ b/src/borg/helpers/parseformat.py
@@ -19,6 +19,7 @@ logger = create_logger()
 
 from .errors import Error
 from .fs import get_keys_dir
+from .msgpack import Timestamp
 from .time import OutputTimestamp, format_time, to_localtime, safe_timestamp, safe_s
 from .. import __version__ as borg_version
 from .. import __version_tuple__ as borg_version_tuple
@@ -1043,6 +1044,8 @@ def prepare_dump_dict(d):
                 value = decode_tuple(value)
             elif isinstance(value, bytes):
                 value = decode_bytes(value)
+            elif isinstance(value, Timestamp):
+                value = value.to_unix_nano()
             if isinstance(key, bytes):
                 key = key.decode()
             res[key] = value
diff --git a/src/borg/item.pyx b/src/borg/item.pyx
index 0b2598ffe..764279db0 100644
--- a/src/borg/item.pyx
+++ b/src/borg/item.pyx
@@ -3,9 +3,9 @@ from collections import namedtuple
 
 from .constants import ITEM_KEYS, ARCHIVE_KEYS
 from .helpers import safe_encode, safe_decode
-from .helpers import bigint_to_int, int_to_bigint
 from .helpers import StableDict
 from .helpers import format_file_size
+from .helpers.msgpack import timestamp_to_int, int_to_timestamp
 
 
 cdef extern from "_item.c":
@@ -171,11 +171,10 @@ class Item(PropDict):
     rdev = PropDict._make_property('rdev', int)
     bsdflags = PropDict._make_property('bsdflags', int)
 
-    # note: we need to keep the bigint conversion for compatibility with borg 1.0 archives.
-    atime = PropDict._make_property('atime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
-    ctime = PropDict._make_property('ctime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
-    mtime = PropDict._make_property('mtime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
-    birthtime = PropDict._make_property('birthtime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
+    atime = PropDict._make_property('atime', int, 'int (ns)', encode=int_to_timestamp, decode=timestamp_to_int)
+    ctime = PropDict._make_property('ctime', int, 'int (ns)', encode=int_to_timestamp, decode=timestamp_to_int)
+    mtime = PropDict._make_property('mtime', int, 'int (ns)', encode=int_to_timestamp, decode=timestamp_to_int)
+    birthtime = PropDict._make_property('birthtime', int, 'int (ns)', encode=int_to_timestamp, decode=timestamp_to_int)
 
     # size is only present for items with a chunk list and then it is sum(chunk_sizes)
     # compatibility note: this is a new feature, in old archives size will be missing.
diff --git a/src/borg/testsuite/item.py b/src/borg/testsuite/item.py
index aa40cc066..80b38edce 100644
--- a/src/borg/testsuite/item.py
+++ b/src/borg/testsuite/item.py
@@ -3,6 +3,7 @@ import pytest
 from ..cache import ChunkListEntry
 from ..item import Item
 from ..helpers import StableDict
+from ..helpers.msgpack import Timestamp
 
 
 def test_item_empty():
@@ -77,15 +78,15 @@ def test_item_int_property():
         item.mode = "invalid"
 
 
-def test_item_bigint_property():
+def test_item_mptimestamp_property():
     item = Item()
     small, big = 42, 2 ** 65
     item.atime = small
     assert item.atime == small
-    assert item.as_dict() == {'atime': small}
+    assert item.as_dict() == {'atime': Timestamp.from_unix_nano(small)}
     item.atime = big
     assert item.atime == big
-    assert item.as_dict() == {'atime': b'\0' * 8 + b'\x02'}
+    assert item.as_dict() == {'atime': Timestamp.from_unix_nano(big)}
 
 
 def test_item_user_group_none():