diff --git a/src/borg/archiver.py b/src/borg/archiver.py
index 68cf0e2f..5a3f1632 100644
--- a/src/borg/archiver.py
+++ b/src/borg/archiver.py
@@ -1518,10 +1518,10 @@ def _info_repository(self, args, repository, manifest, key, cache):
     def do_prune(self, args, repository, manifest, key):
         """Prune repository archives according to specified rules"""
         if not any((args.secondly, args.minutely, args.hourly, args.daily,
-                    args.weekly, args.monthly, args.yearly, args.within)):
+                    args.weekly, args.monthly, args.quarterly, args.yearly, args.within)):
             raise CommandError('At least one of the "keep-within", "keep-last", '
                                '"keep-secondly", "keep-minutely", "keep-hourly", "keep-daily", '
-                               '"keep-weekly", "keep-monthly" or "keep-yearly" settings must be specified.')
+                               '"keep-weekly", "keep-monthly", "keep-quarterly" or "keep-yearly" settings must be specified.')
         if args.prefix is not None:
             args.glob_archives = args.prefix + '*'
         checkpoint_re = r'\.checkpoint(\.\d+)?'
@@ -4715,6 +4715,8 @@ def define_borg_mount(parser):
                                help='number of weekly archives to keep')
         subparser.add_argument('-m', '--keep-monthly', dest='monthly', type=int, default=0,
                                help='number of monthly archives to keep')
+        subparser.add_argument('-q', '--keep-quarterly', dest='quarterly', type=int, default=0,
+                               help='number of quarterly archives to keep')
         subparser.add_argument('-y', '--keep-yearly', dest='yearly', type=int, default=0,
                                help='number of yearly archives to keep')
         define_archive_filters_group(subparser, sort_by=False, first_last=False)
diff --git a/src/borg/helpers/misc.py b/src/borg/helpers/misc.py
index b62e066b..ae4f7743 100644
--- a/src/borg/helpers/misc.py
+++ b/src/borg/helpers/misc.py
@@ -31,21 +31,50 @@ def prune_within(archives, hours, kept_because):
     return result
 
 
+def default_period_func(pattern):
+    def inner(a):
+        return to_localtime(a.ts).strftime(pattern)
+
+    return inner
+
+
+def quarterly_period_func(a):
+    (year, week, _) = to_localtime(a.ts).isocalendar()
+    if week <= 13:
+        # Weeks containing Jan 4th to Mar 28th (leap year) or 29th- 91 (13*7)
+        # days later.
+        return (year, 1)
+    elif week > 13 and week <= 26:
+        # Weeks containing Apr 4th (leap year) or 5th to Jun 27th or 28th- 91
+        # days later
+        return (year, 2)
+    elif week > 26 and week <= 39:
+        # Weeks containing Jul 4th (leap year) or 5th to Sep 26th or 27th-
+        # at least 91 days later
+        return (year, 3)
+    else:
+        # Everything else, Oct 3rd (leap year) or 4th onward, will always
+        # include week of Dec 26th (leap year) or Dec 27th, may also include
+        # up to possibly Jan 3rd of next year.
+        return (year, 4)
+
+
 PRUNING_PATTERNS = OrderedDict([
-    ("secondly", '%Y-%m-%d %H:%M:%S'),
-    ("minutely", '%Y-%m-%d %H:%M'),
-    ("hourly", '%Y-%m-%d %H'),
-    ("daily", '%Y-%m-%d'),
-    ("weekly", '%G-%V'),
-    ("monthly", '%Y-%m'),
-    ("yearly", '%Y'),
+    ("secondly", default_period_func('%Y-%m-%d %H:%M:%S')),
+    ("minutely", default_period_func('%Y-%m-%d %H:%M')),
+    ("hourly", default_period_func('%Y-%m-%d %H')),
+    ("daily", default_period_func('%Y-%m-%d')),
+    ("weekly", default_period_func('%G-%V')),
+    ("monthly", default_period_func('%Y-%m')),
+    ("quarterly", quarterly_period_func),
+    ("yearly", default_period_func('%Y')),
 ])
 
 
 def prune_split(archives, rule, n, kept_because=None):
     last = None
     keep = []
-    pattern = PRUNING_PATTERNS[rule]
+    period_func = PRUNING_PATTERNS[rule]
     if kept_because is None:
         kept_because = {}
     if n == 0:
@@ -53,7 +82,7 @@ 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)
+        period = period_func(a)
         if period != last:
             last = period
             if a.id not in kept_because:
diff --git a/src/borg/testsuite/conftest.py b/src/borg/testsuite/conftest.py
index bc40f33b..4c99b822 100644
--- a/src/borg/testsuite/conftest.py
+++ b/src/borg/testsuite/conftest.py
@@ -1,6 +1,7 @@
 import os
 
 import pytest
+from packaging.version import parse as parse_version, Version
 
 # IMPORTANT keep this above all other borg imports to avoid inconsistent values
 # for `from borg.constants import PBKDF2_ITERATIONS` (or star import) usages before
@@ -37,8 +38,7 @@ def clean_env(tmpdir_factory, monkeypatch):
     for key in keys:
         monkeypatch.delenv(key, raising=False)
 
-
-def pytest_report_header(config, start_path):
+def _pytest_report_header(config, start_path):
     tests = {
         "BSD flags": has_lchflags,
         "fuse2": has_llfuse,
@@ -60,6 +60,15 @@ def pytest_report_header(config, start_path):
     output += "Tests disabled: " + ", ".join(disabled)
     return output
 
+# Avoid "Argument(s) {'start_path'} are declared in the hookimpl but can not
+# be found in the hookspec" for pytest 6.2.x.
+if parse_version(pytest.__version__) < Version("7.0.0"):
+    def pytest_report_header(config):
+        _pytest_report_header(config, None)
+else:
+    def pytest_report_header(config, start_path):
+        _pytest_report_header(config, start_path)
+
 
 class DefaultPatches:
     def __init__(self, request):