diff --git a/man/systemd.timer.xml b/man/systemd.timer.xml
index fca11b2d04c..040b8e28939 100644
--- a/man/systemd.timer.xml
+++ b/man/systemd.timer.xml
@@ -163,7 +163,10 @@
timers defined in the other directives.
These are monotonic timers, independent of wall-clock time and timezones. If the computer is
- temporarily suspended, the monotonic clock pauses, too.
+ temporarily suspended, the monotonic clock generally pauses, too. Note that if
+ WakeSystem= is used, a different monotonic clock is selected that continues to
+ advance while the system is suspended and thus can be used as the trigger to resume the
+ system.
If the empty string is assigned to any of these options, the list of timers is reset (both
monotonic timers and OnCalendar= timers, see below), and all prior assignments
@@ -316,7 +319,16 @@
false.
Note that this functionality requires privileges and is thus generally only available in the
- system service manager.
+ system service manager.
+
+ Note that behaviour of monotonic clock timers (as configured with
+ OnActiveSec=, OnBootSec=, OnStartupSec=,
+ OnUnitActiveSec=, OnUnitInactiveSec=, see above) is altered
+ depending on this option. If false, a monotonic clock is used that is paused during system suspend
+ (CLOCK_MONOTONIC), if true a different monotonic clock is used that continues
+ advancing during system suspend (CLOCK_BOOTTIME), see
+ clock_getres2 for
+ details.