diff --git a/qubes-rpc/qubes-sync-clock b/qubes-rpc/qubes-sync-clock
index de508f1e6..7065efb3c 100755
--- a/qubes-rpc/qubes-sync-clock
+++ b/qubes-rpc/qubes-sync-clock
@@ -18,21 +18,49 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 #
 
-import sys
+import os
 import re
 import subprocess
+import sys
 
 def main():
-    stdin = sys.stdin.read(25)
-
-    untrusted_date_out = stdin.strip()
-
-    if not re.match(r'^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\+00:?00$', untrusted_date_out):
+    os.environ['LC_ALL'] = 'C'
+    untrusted_date_out = sys.stdin.buffer.read(36)
+    try:
+        untrusted_date_out.decode('ascii', 'strict')
+    except UnicodeDecodeError:
+        sys.stderr.write('Received non-ASCII date, aborting!\n')
+        sys.exit(1)
+    untrusted_date_len = len(untrusted_date_out)
+    if untrusted_date_len == 36: # new format, nanosecond precision
+        regexp = rb'\A\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2},[0-9]{9}\+00:00\n\Z'
+        precision = b'ns'
+    elif untrusted_date_len == 26: # old format, second precision
+        regexp = rb'\A\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\+00:00\n\Z'
+        precision = b'seconds'
+    else:
+        sys.stderr.write('Invalid date length (expected 26 or 36 bytes, got {})'
+                         ', aborting!\n'.format(untrusted_date_len))
+        sys.exit(1)
+    if untrusted_date_out[-7:] != b'+00:00\n':
+        sys.stderr.write('Date not in UTC, aborting!\n')
+        sys.exit(1)
+    if not re.match(regexp, untrusted_date_out):
         sys.stderr.write('Invalid date received, aborting!\n')
         sys.exit(1)
+    # this time is arbitrary, something better should be used instead
+    if untrusted_date_out[:19] <= b'2022-07-10T17:08:31':
+        sys.stderr.write('Received a date older than this program, aborting!\n')
+        sys.exit(1)
     date_out = untrusted_date_out
-    subprocess.check_call(['date', '-u', '-Iseconds', '-s', date_out],
-        stdout=subprocess.DEVNULL)
+    try:
+        subprocess.check_call([b'date', b'-u', b'-I' + precision, b'-s',
+                               date_out[:-1]],
+            stdout=subprocess.DEVNULL)
+    except subprocess.CalledProcessError as e:
+        # input is trusted here, so it can be safely printed
+        sys.stderr.write('Unable to set the date: process {!r} failed.\n'.format(e.cmd))
+        sys.exit(e.returncode)
 
 if __name__ == '__main__':
     main()
diff --git a/qubes-rpc/qubes.GetDate b/qubes-rpc/qubes.GetDate
index ebd9ebf90..bb3af9b0f 100755
--- a/qubes-rpc/qubes.GetDate
+++ b/qubes-rpc/qubes.GetDate
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/sh --
 #
 # The Qubes OS Project, http://www.qubes-os.org
 #
@@ -16,7 +16,9 @@
 # You should have received a copy of the GNU General Public License
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
-#
-#
 
-date -u -Iseconds
+export LC_ALL=C
+case ${1-} in
+'') exec date -u -Iseconds;;
+nanosecond|nanoseconds|ns|*) exec date -u -Ins;;
+esac
diff --git a/qubes-rpc/qvm-sync-clock b/qubes-rpc/qvm-sync-clock
index eaaf6f69d..9f0b0c0db 100644
--- a/qubes-rpc/qvm-sync-clock
+++ b/qubes-rpc/qvm-sync-clock
@@ -19,4 +19,5 @@
 #
 
 # shellcheck disable=SC2016
-qrexec-client-vm '$default' qubes.GetDate /usr/lib/qubes/qubes-sync-clock
+qrexec-client-vm --filter-escape-chars-stderr '@default' \
+    qubes.GetDate+nanoseconds /usr/lib/qubes/qubes-sync-clock
diff --git a/vm-systemd/qubes-sync-time.service b/vm-systemd/qubes-sync-time.service
index e611a42ab..f802ce5fe 100644
--- a/vm-systemd/qubes-sync-time.service
+++ b/vm-systemd/qubes-sync-time.service
@@ -5,4 +5,5 @@ ConditionPathExists=!/var/run/qubes-service/clocksync
 
 [Service]
 ExecStart=/usr/bin/qvm-sync-clock
+Type=oneshot
 User=root