Fix the test failing due to timestamp localisation, fixes #4853

from https://borgbackup.readthedocs.io/en/stable/usage/general.html#date-and-time

    Unless otherwise noted, we display local date and time.
    Internally, we store and process date and time as UTC.

OK, that does not directly say something about --timestamp, but as the cli is also part of the user interface (as output is), this might mean that maybe not the test needs fixing, but our processing of that option.

But, the docs also say:

    --timestamp TIMESTAMP
    manually specify the archive creation date/time (UTC,  yyyy-mm-ddThh:mm:ss format).
    Alternatively, give a reference  file/directory.

So, using UTC there is a documented feature, although it is different from output using localtime.

So, the test fix in this PR is correct according to the docs. \o/

src/borg/testsuite/archiver.py

@@ -18,6 +18,7 @@ import unittest
 from binascii import unhexlify, b2a_base64
 from configparser import ConfigParser
 from datetime import datetime
+from datetime import timezone
 from datetime import timedelta
 from hashlib import sha256
 from io import BytesIO, StringIO
@@ -2552,6 +2553,7 @@ class ArchiverTestCase(ArchiverTestCaseBase):
         assert sha256_before == sha256_after
 
     def test_recreate_timestamp(self):
+        local_timezone = datetime.now(timezone(timedelta(0))).astimezone().tzinfo
         self.create_test_files()
         self.cmd('init', '--encryption=repokey', self.repository_location)
         archive = self.repository_location + '::test0'
@@ -2559,8 +2561,10 @@ class ArchiverTestCase(ArchiverTestCaseBase):
         self.cmd('recreate', '--timestamp', "1970-01-02T00:00:00", '--comment',
                  'test', archive)
         info = self.cmd('info', archive).splitlines()
-        assert any([re.search(r'Time \(start\).+ 1970-01-02', item) for item in info])
-        assert any([re.search(r'Time \(end\).+ 1970-01-02', item) for item in info])
+        dtime = datetime(1970, 1, 2) + local_timezone.utcoffset(None)
+        s_time = dtime.strftime("%Y-%m-%d")
+        assert any([re.search(r'Time \(start\).+ %s' % s_time, item) for item in info])
+        assert any([re.search(r'Time \(end\).+ %s' % s_time, item) for item in info])
 
     def test_recreate_dry_run(self):
         self.create_regular_file('compressible', size=10000)