diff --git a/src/borg/archive.py b/src/borg/archive.py
index bed8b7012..e9fd05d12 100644
--- a/src/borg/archive.py
+++ b/src/borg/archive.py
@@ -6,7 +6,7 @@ import sys
 import time
 from collections import OrderedDict
 from contextlib import contextmanager
-from datetime import datetime, timezone, timedelta
+from datetime import datetime, timedelta
 from functools import partial
 from getpass import getuser
 from io import BytesIO
@@ -479,13 +479,13 @@ class Archive:
             start_monotonic is None
         ), "Logic error: if start is given, start_monotonic must be given as well and vice versa."
         if start is None:
-            start = datetime.utcnow()
+            start = datetime.now().astimezone()  # local time with local timezone
             start_monotonic = time.monotonic()
         self.chunker_params = chunker_params
         self.start = start
         self.start_monotonic = start_monotonic
         if end is None:
-            end = datetime.utcnow()
+            end = datetime.now().astimezone()  # local time with local timezone
         self.end = end
         self.consider_part_files = consider_part_files
         self.pipeline = DownloadPipeline(self.repository, self.key)
@@ -549,8 +549,8 @@ class Archive:
     def info(self):
         if self.create:
             stats = self.stats
-            start = self.start.replace(tzinfo=timezone.utc)
-            end = self.end.replace(tzinfo=timezone.utc)
+            start = self.start
+            end = self.end
         else:
             stats = self.calc_stats(self.cache)
             start = self.ts
@@ -587,8 +587,8 @@ Time (end):   {end}
 Duration: {0.duration}
 """.format(
             self,
-            start=OutputTimestamp(self.start.replace(tzinfo=timezone.utc)),
-            end=OutputTimestamp(self.end.replace(tzinfo=timezone.utc)),
+            start=OutputTimestamp(self.start),
+            end=OutputTimestamp(self.end),
             location=self.repository._location.canonical_path(),
         )
 
@@ -629,11 +629,11 @@ Duration: {0.duration}
         item_ptrs = archive_put_items(self.items_buffer.chunks, key=self.key, cache=self.cache, stats=self.stats)
         duration = timedelta(seconds=time.monotonic() - self.start_monotonic)
         if timestamp is None:
-            end = datetime.utcnow()
+            end = datetime.now().astimezone()  # local time with local timezone
             start = end - duration
         else:
-            end = timestamp + duration
             start = timestamp
+            end = start + duration
         self.start = start
         self.end = end
         metadata = {
@@ -2314,7 +2314,7 @@ class ArchiveRecreater:
             target.rename(archive.name)
         if self.stats:
             target.start = _start
-            target.end = datetime.utcnow()
+            target.end = datetime.now().astimezone()  # local time with local timezone
             log_multi(str(target), str(target.stats))
 
     def matcher_add_tagged_dirs(self, archive):
diff --git a/src/borg/archiver/create.py b/src/borg/archiver/create.py
index 42b9d52bd..0030fabce 100644
--- a/src/borg/archiver/create.py
+++ b/src/borg/archiver/create.py
@@ -204,7 +204,7 @@ class CreateMixIn:
         self.noxattrs = args.noxattrs
         self.exclude_nodump = args.exclude_nodump
         dry_run = args.dry_run
-        t0 = datetime.utcnow()
+        t0 = datetime.now().astimezone()  # local time with local timezone
         t0_monotonic = time.monotonic()
         logger.info('Creating archive at "%s"' % args.location.processed)
         if not dry_run:
@@ -821,8 +821,8 @@ class CreateMixIn:
             dest="timestamp",
             type=timestamp,
             default=None,
-            help="manually specify the archive creation date/time (UTC, yyyy-mm-ddThh:mm:ss format). "
-            "Alternatively, give a reference file/directory.",
+            help="manually specify the archive creation date/time (yyyy-mm-ddThh:mm:ss[(+|-)HH:MM] format, "
+            "(+|-)HH:MM is the UTC offset, default: +00:00). Alternatively, give a reference file/directory.",
         )
         archive_group.add_argument(
             "-c",
diff --git a/src/borg/archiver/help.py b/src/borg/archiver/help.py
index 4b5de0650..899cda3c6 100644
--- a/src/borg/archiver/help.py
+++ b/src/borg/archiver/help.py
@@ -291,7 +291,7 @@ class HelpMixIn:
         Examples::
 
             borg create /path/to/repo::{hostname}-{user}-{utcnow} ...
-            borg create /path/to/repo::{hostname}-{now:%Y-%m-%d_%H:%M:%S} ...
+            borg create /path/to/repo::{hostname}-{now:%Y-%m-%d_%H:%M:%S%z} ...
             borg prune -a '{hostname}-*' ...
 
         .. note::
diff --git a/src/borg/archiver/recreate.py b/src/borg/archiver/recreate.py
index 3a0a64dbd..2b10366ca 100644
--- a/src/borg/archiver/recreate.py
+++ b/src/borg/archiver/recreate.py
@@ -177,8 +177,8 @@ class RecreateMixIn:
             dest="timestamp",
             type=timestamp,
             default=None,
-            help="manually specify the archive creation date/time (UTC, yyyy-mm-ddThh:mm:ss format). "
-            "alternatively, give a reference file/directory.",
+            help="manually specify the archive creation date/time (yyyy-mm-ddThh:mm:ss[(+|-)HH:MM] format, "
+            "(+|-)HH:MM is the UTC offset, default: +00:00). Alternatively, give a reference file/directory.",
         )
         archive_group.add_argument(
             "-C",
diff --git a/src/borg/archiver/tar.py b/src/borg/archiver/tar.py
index be35f58b6..f9ecb91a9 100644
--- a/src/borg/archiver/tar.py
+++ b/src/borg/archiver/tar.py
@@ -238,7 +238,7 @@ class TarMixIn:
         return self.exit_code
 
     def _import_tar(self, args, repository, manifest, key, cache, tarstream):
-        t0 = datetime.utcnow()
+        t0 = datetime.now().astimezone()  # local time with local timezone
         t0_monotonic = time.monotonic()
 
         archive = Archive(
@@ -485,8 +485,8 @@ class TarMixIn:
             type=timestamp,
             default=None,
             metavar="TIMESTAMP",
-            help="manually specify the archive creation date/time (UTC, yyyy-mm-ddThh:mm:ss format). "
-            "alternatively, give a reference file/directory.",
+            help="manually specify the archive creation date/time (yyyy-mm-ddThh:mm:ss[(+|-)HH:MM] format, "
+            "(+|-)HH:MM is the UTC offset, default: +00:00). Alternatively, give a reference file/directory.",
         )
         archive_group.add_argument(
             "-c",
diff --git a/src/borg/helpers/__init__.py b/src/borg/helpers/__init__.py
index cea471506..b694d5bf4 100644
--- a/src/borg/helpers/__init__.py
+++ b/src/borg/helpers/__init__.py
@@ -36,7 +36,7 @@ from .process import signal_handler, raising_signal_handler, sig_int, ignore_sig
 from .process import popen_with_error_handling, is_terminal, prepare_subprocess_env, create_filter_process
 from .progress import ProgressIndicatorPercent, ProgressIndicatorEndless, ProgressIndicatorMessage
 from .time import parse_timestamp, timestamp, safe_timestamp, safe_s, safe_ns, MAX_S, SUPPORT_32BIT_PLATFORMS
-from .time import format_time, format_timedelta, isoformat_time, to_localtime, OutputTimestamp
+from .time import format_time, format_timedelta, OutputTimestamp
 from .yes_no import yes, TRUISH, FALSISH, DEFAULTISH
 
 from .msgpack import is_slow_msgpack, is_supported_msgpack, get_limited_unpacker
diff --git a/src/borg/helpers/manifest.py b/src/borg/helpers/manifest.py
index c28c1ee73..704902136 100644
--- a/src/borg/helpers/manifest.py
+++ b/src/borg/helpers/manifest.py
@@ -3,7 +3,7 @@ import os
 import os.path
 import re
 from collections import abc, namedtuple
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from operator import attrgetter
 from typing import Sequence, FrozenSet
 
@@ -65,7 +65,7 @@ class Archives(abc.MutableMapping):
         id, ts = info
         assert isinstance(id, bytes)
         if isinstance(ts, datetime):
-            ts = ts.replace(tzinfo=None).isoformat(timespec="microseconds")
+            ts = ts.isoformat(timespec="microseconds")
         assert isinstance(ts, str)
         self._archives[name] = {"id": id, "time": ts}
 
@@ -180,7 +180,7 @@ class Manifest:
 
     @property
     def last_timestamp(self):
-        return parse_timestamp(self.timestamp, tzinfo=None)
+        return parse_timestamp(self.timestamp)
 
     @classmethod
     def load(cls, repository, operations, key=None, force_tam_not_required=False):
@@ -254,11 +254,12 @@ class Manifest:
             self.config["tam_required"] = True
         # self.timestamp needs to be strictly monotonically increasing. Clocks often are not set correctly
         if self.timestamp is None:
-            self.timestamp = datetime.utcnow().isoformat(timespec="microseconds")
+            self.timestamp = datetime.now(tz=timezone.utc).isoformat(timespec="microseconds")
         else:
-            prev_ts = self.last_timestamp
-            incremented = (prev_ts + timedelta(microseconds=1)).isoformat(timespec="microseconds")
-            self.timestamp = max(incremented, datetime.utcnow().isoformat(timespec="microseconds"))
+            incremented_ts = self.last_timestamp + timedelta(microseconds=1)
+            now_ts = datetime.now(tz=timezone.utc)
+            max_ts = max(incremented_ts, now_ts)
+            self.timestamp = max_ts.isoformat(timespec="microseconds")
         # include checks for limits as enforced by limited unpacker (used by load())
         assert len(self.archives) <= MAX_ARCHIVES
         assert all(len(name) <= 255 for name in self.archives)
diff --git a/src/borg/helpers/misc.py b/src/borg/helpers/misc.py
index 3143540a4..60760598a 100644
--- a/src/borg/helpers/misc.py
+++ b/src/borg/helpers/misc.py
@@ -13,7 +13,6 @@ from ..logger import create_logger
 
 logger = create_logger()
 
-from .time import to_localtime
 from . import msgpack
 from .. import __version__ as borg_version
 from .. import chunker
@@ -55,7 +54,8 @@ def prune_split(archives, rule, n, kept_because=None):
 
     a = None
     for a in sorted(archives, key=attrgetter("ts"), reverse=True):
-        period = to_localtime(a.ts).strftime(pattern)
+        # we compute the pruning in local time zone
+        period = a.ts.astimezone().strftime(pattern)
         if period != last:
             last = period
             if a.id not in kept_because:
diff --git a/src/borg/helpers/parseformat.py b/src/borg/helpers/parseformat.py
index a561e90cd..5f40cbe26 100644
--- a/src/borg/helpers/parseformat.py
+++ b/src/borg/helpers/parseformat.py
@@ -21,7 +21,7 @@ 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
+from .time import OutputTimestamp, format_time, safe_timestamp
 from .. import __version__ as borg_version
 from .. import __version_tuple__ as borg_version_tuple
 from ..constants import *  # NOQA
@@ -196,7 +196,7 @@ def replace_placeholders(text, overrides={}):
         "fqdn": fqdn,
         "reverse-fqdn": ".".join(reversed(fqdn.split("."))),
         "hostname": hostname,
-        "now": DatetimeWrapper(current_time.astimezone(None)),
+        "now": DatetimeWrapper(current_time.astimezone()),
         "utcnow": DatetimeWrapper(current_time),
         "user": getosusername(),
         "uuid4": str(uuid.uuid4()),
@@ -303,7 +303,7 @@ def sizeof_fmt_decimal(num, suffix="B", sep="", precision=2, sign=False):
 
 
 def format_archive(archive):
-    return "%-36s %s [%s]" % (archive.name, format_time(to_localtime(archive.ts)), bin_to_hex(archive.id))
+    return "%-36s %s [%s]" % (archive.name, format_time(archive.ts), bin_to_hex(archive.id))
 
 
 def parse_stringified_list(s):
@@ -500,9 +500,13 @@ class Location:
             )
 
     def with_timestamp(self, timestamp):
+        # note: this only affects the repository URL/path, not the archive name!
         return Location(
             self.raw,
-            overrides={"now": DatetimeWrapper(timestamp.astimezone(None)), "utcnow": DatetimeWrapper(timestamp)},
+            overrides={
+                "now": DatetimeWrapper(timestamp),
+                "utcnow": DatetimeWrapper(timestamp.astimezone(timezone.utc)),
+            },
         )
 
 
@@ -973,7 +977,7 @@ def basic_json_data(manifest, *, cache=None, extra=None):
     key = manifest.key
     data = extra or {}
     data.update({"repository": BorgJsonEncoder().default(manifest.repository), "encryption": {"mode": key.ARG_NAME}})
-    data["repository"]["last_modified"] = OutputTimestamp(manifest.last_timestamp.replace(tzinfo=timezone.utc))
+    data["repository"]["last_modified"] = OutputTimestamp(manifest.last_timestamp)
     if key.NAME.startswith("key file"):
         data["encryption"]["keyfile"] = key.find_key()
     if cache:
diff --git a/src/borg/helpers/time.py b/src/borg/helpers/time.py
index 0b18de14a..ac1506f30 100644
--- a/src/borg/helpers/time.py
+++ b/src/borg/helpers/time.py
@@ -1,17 +1,11 @@
 import os
-import time
 from datetime import datetime, timezone
 
 
-def to_localtime(ts):
-    """Convert datetime object from UTC to local time zone"""
-    return datetime(*time.localtime((ts - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds())[:6])
-
-
 def parse_timestamp(timestamp, tzinfo=timezone.utc):
     """Parse a ISO 8601 timestamp string"""
     dt = datetime.fromisoformat(timestamp)
-    if tzinfo is not None:
+    if dt.tzinfo is None:
         dt = dt.replace(tzinfo=tzinfo)
     return dt
 
@@ -24,10 +18,7 @@ def timestamp(s):
         return datetime.fromtimestamp(ts, tz=timezone.utc)
     except OSError:
         # didn't work, try parsing as a ISO timestamp. if no TZ is given, we assume UTC.
-        dt = datetime.fromisoformat(s)
-        if dt.tzinfo is None:
-            dt = dt.replace(tzinfo=timezone.utc)
-        return dt
+        return parse_timestamp(s)
 
 
 # Not too rarely, we get crappy timestamps from the fs, that overflow some computations.
@@ -84,15 +75,7 @@ def format_time(ts: datetime, format_spec=""):
     """
     Convert *ts* to a human-friendly format with textual weekday.
     """
-    return ts.strftime("%a, %Y-%m-%d %H:%M:%S" if format_spec == "" else format_spec)
-
-
-def isoformat_time(ts: datetime):
-    """
-    Format *ts* according to ISO 8601.
-    """
-    # note: first make all datetime objects tz aware before adding %z here.
-    return ts.isoformat(timespec="microseconds")
+    return ts.strftime("%a, %Y-%m-%d %H:%M:%S %z" if format_spec == "" else format_spec)
 
 
 def format_timedelta(td):
@@ -113,8 +96,6 @@ def format_timedelta(td):
 
 class OutputTimestamp:
     def __init__(self, ts: datetime):
-        if ts.tzinfo == timezone.utc:
-            ts = to_localtime(ts)
         self.ts = ts
 
     def __format__(self, format_spec):
@@ -124,6 +105,6 @@ class OutputTimestamp:
         return f"{self}"
 
     def isoformat(self):
-        return isoformat_time(self.ts)
+        return self.ts.isoformat(timespec="microseconds")
 
     to_json = isoformat
diff --git a/src/borg/repository.py b/src/borg/repository.py
index d55e2d9e6..6518c0174 100644
--- a/src/borg/repository.py
+++ b/src/borg/repository.py
@@ -8,7 +8,7 @@ import time
 from binascii import hexlify, unhexlify
 from collections import defaultdict
 from configparser import ConfigParser
-from datetime import datetime
+from datetime import datetime, timezone
 from functools import partial
 from itertools import islice
 
@@ -657,7 +657,7 @@ class Repository:
             with open(os.path.join(self.path, "transactions"), "a") as log:
                 print(
                     "transaction %d, UTC time %s"
-                    % (transaction_id, datetime.utcnow().isoformat(timespec="microseconds")),
+                    % (transaction_id, datetime.now(tz=timezone.utc).isoformat(timespec="microseconds")),
                     file=log,
                 )
 
diff --git a/src/borg/testsuite/archiver.py b/src/borg/testsuite/archiver.py
index 33eb48122..dd8fa48e3 100644
--- a/src/borg/testsuite/archiver.py
+++ b/src/borg/testsuite/archiver.py
@@ -18,9 +18,7 @@ import time
 import unittest
 from binascii import unhexlify, b2a_base64, a2b_base64
 from configparser import ConfigParser
-from datetime import datetime
-from datetime import timezone
-from datetime import timedelta
+from datetime import datetime, timezone, timedelta
 from hashlib import sha256
 from io import BytesIO, StringIO
 from unittest.mock import patch
@@ -251,7 +249,7 @@ def test_disk_full(cmd):
 
 def checkts(ts):
     # check if the timestamp is in the expected format
-    assert datetime.strptime(ts, ISO_FORMAT)  # must not raise
+    assert datetime.strptime(ts, ISO_FORMAT + "%z")  # must not raise
 
 
 class ArchiverTestCaseBase(BaseTestCase):
@@ -2596,7 +2594,6 @@ class ArchiverTestCase(ArchiverTestCaseBase):
         file1 = items[1]
         assert file1["path"] == "input/file1"
         assert file1["size"] == 81920
-        checkts(file1["mtime"])
 
         list_archive = self.cmd(
             f"--repo={self.repository_location}", "list", "test", "--json-lines", "--format={sha256}"
@@ -4063,7 +4060,9 @@ class ManifestAuthenticationTest(ArchiverTestCaseBase):
                             "version": 1,
                             "archives": {},
                             "config": {},
-                            "timestamp": (datetime.utcnow() + timedelta(days=1)).isoformat(timespec="microseconds"),
+                            "timestamp": (datetime.now(tz=timezone.utc) + timedelta(days=1)).isoformat(
+                                timespec="microseconds"
+                            ),
                         }
                     ),
                 ),
@@ -4083,7 +4082,9 @@ class ManifestAuthenticationTest(ArchiverTestCaseBase):
                         {
                             "version": 1,
                             "archives": {},
-                            "timestamp": (datetime.utcnow() + timedelta(days=1)).isoformat(timespec="microseconds"),
+                            "timestamp": (datetime.now(tz=timezone.utc) + timedelta(days=1)).isoformat(
+                                timespec="microseconds"
+                            ),
                         }
                     ),
                 ),