diff --git a/bin/tests/system/doth/tests_gnutls.py b/bin/tests/system/doth/tests_gnutls.py
index 8770206fa8..f49b4401c5 100644
--- a/bin/tests/system/doth/tests_gnutls.py
+++ b/bin/tests/system/doth/tests_gnutls.py
@@ -72,11 +72,11 @@ def test_gnutls_cli_query(gnutls_cli_executable, named_tlsport):
         # upon receiving a DNS response.
         selector = selectors.DefaultSelector()
         selector.register(gnutls_cli.stdout, selectors.EVENT_READ)
-        deadline = time.time() + 10
+        deadline = time.monotonic() + 10
         gnutls_cli_output = b""
         response = b""
         while not response and not gnutls_cli.poll():
-            if not selector.select(timeout=deadline - time.time()):
+            if not selector.select(timeout=deadline - time.monotonic()):
                 break
             gnutls_cli_output += gnutls_cli.stdout.read(512)
             try:
diff --git a/bin/tests/system/isctest/log/watchlog.py b/bin/tests/system/isctest/log/watchlog.py
index b17cd0597f..ffa75e156d 100644
--- a/bin/tests/system/isctest/log/watchlog.py
+++ b/bin/tests/system/isctest/log/watchlog.py
@@ -229,8 +229,8 @@ class WatchLog(abc.ABC):
             raise WatchLogException("No file to watch")
         leftover = ""
         assert timeout, "Do not use this class unless you want to WAIT for something."
-        deadline = time.time() + timeout
-        while time.time() < deadline:
+        deadline = time.monotonic() + timeout
+        while time.monotonic() < deadline:
             for line in self._fd.readlines():
                 if line[-1] != "\n":
                     # Line is not completely written yet, buffer and keep on waiting
diff --git a/bin/tests/system/isctest/run.py b/bin/tests/system/isctest/run.py
index b26190e4a3..5c994ce377 100644
--- a/bin/tests/system/isctest/run.py
+++ b/bin/tests/system/isctest/run.py
@@ -126,9 +126,9 @@ def perl(script: str, args: Optional[List[str]] = None) -> None:
 
 
 def retry_with_timeout(func, timeout, delay=1, msg=None):
-    start_time = time.time()
+    start_time = time.monotonic()
     exc_msg = None
-    while time.time() < start_time + timeout:
+    while time.monotonic() < start_time + timeout:
         exc_msg = None
         try:
             if func():
diff --git a/bin/tests/system/pipelined/ans5/ans.py b/bin/tests/system/pipelined/ans5/ans.py
index bac5ed35d8..b58ad84bef 100644
--- a/bin/tests/system/pipelined/ans5/ans.py
+++ b/bin/tests/system/pipelined/ans5/ans.py
@@ -84,7 +84,7 @@ class TCPDelayer(threading.Thread):
         while self.running:
             curr_timeout = 0.5
             try:
-                curr_timeout = self.queue[0][0] - time.time()
+                curr_timeout = self.queue[0][0] - time.monotonic()
             except StopIteration:
                 pass
             if curr_timeout > 0:
@@ -97,14 +97,14 @@ class TCPDelayer(threading.Thread):
                     data = self.conn.recv(65535)
                     if not data:
                         return
-                    self.queue.append((time.time() + DELAY, data))
+                    self.queue.append((time.monotonic() + DELAY, data))
                 if self.cconn in rfds:
                     data = self.cconn.recv(65535)
                     if not data == 0:
                         return
                     self.conn.send(data)
             try:
-                while self.queue[0][0] - time.time() < 0:
+                while self.queue[0][0] - time.monotonic() < 0:
                     _, data = self.queue.pop(0)
                     self.cconn.send(data)
             except StopIteration:
@@ -133,7 +133,7 @@ class UDPDelayer(threading.Thread):
         while self.running:
             curr_timeout = 0.5
             if self.queue:
-                curr_timeout = self.queue[0][0] - time.time()
+                curr_timeout = self.queue[0][0] - time.monotonic()
             if curr_timeout >= 0:
                 if curr_timeout == 0:
                     curr_timeout = 0.5
@@ -144,7 +144,7 @@ class UDPDelayer(threading.Thread):
                     data, addr = self.sock.recvfrom(65535)
                     if not data:
                         return
-                    self.queue.append((time.time() + DELAY, data))
+                    self.queue.append((time.monotonic() + DELAY, data))
                     qid = struct.unpack(">H", data[:2])[0]
                     log("Received a query from %s, queryid %d" % (str(addr), qid))
                     self.qid_mapping[qid] = addr
@@ -160,7 +160,7 @@ class UDPDelayer(threading.Thread):
                             "Received a response from %s, queryid %d, sending to %s"
                             % (str(addr), qid, str(dst))
                         )
-            while self.queue and self.queue[0][0] - time.time() < 0:
+            while self.queue and self.queue[0][0] - time.monotonic() < 0:
                 _, data = self.queue.pop(0)
                 qid = struct.unpack(">H", data[:2])[0]
                 log("Sending a query to %s, queryid %d" % (str(self.dst), qid))
diff --git a/bin/tests/system/tcp/ans6/ans.py b/bin/tests/system/tcp/ans6/ans.py
index 4595ddcd07..b94697e2cd 100644
--- a/bin/tests/system/tcp/ans6/ans.py
+++ b/bin/tests/system/tcp/ans6/ans.py
@@ -71,9 +71,9 @@ def open_connections(active_conns, count, host, port):
         else:
             queued.append(sock)
 
-    start = time.time()
+    start = time.monotonic()
     while queued:
-        now = time.time()
+        now = time.monotonic()
         time_left = OPEN_TIMEOUT - (now - start)
         if time_left <= 0:
             break