diff --git a/systemd/systemd.go b/systemd/systemd.go
index 7c518de..43345d0 100644
--- a/systemd/systemd.go
+++ b/systemd/systemd.go
@@ -67,6 +67,7 @@ type Collector struct {
 	unitTasksCurrentDesc          *prometheus.Desc
 	unitTasksMaxDesc              *prometheus.Desc
 	unitActiveEnterTimeDesc       *prometheus.Desc
+	unitActiveEnterMonotonicDesc  *prometheus.Desc
 	unitActiveExitTimeDesc        *prometheus.Desc
 	unitInactiveEnterTimeDesc     *prometheus.Desc
 	unitInactiveExitTimeDesc      *prometheus.Desc
@@ -140,6 +141,11 @@ func NewCollector(logger *slog.Logger) (*Collector, error) {
 		"Last time the unit transitioned into the active state",
 		[]string{"name", "type"}, nil,
 	)
+	unitActiveEnterMonotonicDesc := prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "", "unit_active_enter_monotonic_seconds"),
+		"Monotonic time when the unit transitioned into the active state",
+		[]string{"name", "type"}, nil,
+	)
 	unitActiveExitTimeDesc := prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, "", "unit_active_exit_time_seconds"),
 		"Last time the unit transitioned out of the active state",
@@ -237,6 +243,7 @@ func NewCollector(logger *slog.Logger) (*Collector, error) {
 		unitTasksCurrentDesc:          unitTasksCurrentDesc,
 		unitTasksMaxDesc:              unitTasksMaxDesc,
 		unitActiveEnterTimeDesc:       unitActiveEnterTimeDesc,
+		unitActiveEnterMonotonicDesc:  unitActiveEnterMonotonicDesc,
 		unitActiveExitTimeDesc:        unitActiveExitTimeDesc,
 		unitInactiveEnterTimeDesc:     unitInactiveEnterTimeDesc,
 		unitInactiveExitTimeDesc:      unitInactiveExitTimeDesc,
@@ -276,6 +283,11 @@ func (c *Collector) Describe(desc chan<- *prometheus.Desc) {
 	desc <- c.unitStartTimeDesc
 	desc <- c.unitTasksCurrentDesc
 	desc <- c.unitTasksMaxDesc
+	desc <- c.unitActiveEnterTimeDesc
+	desc <- c.unitActiveEnterMonotonicDesc
+	desc <- c.unitActiveExitTimeDesc
+	desc <- c.unitInactiveEnterTimeDesc
+	desc <- c.unitInactiveExitTimeDesc
 	desc <- c.nRestartsDesc
 	desc <- c.timerLastTriggerDesc
 	desc <- c.socketAcceptedConnectionsDesc
@@ -473,6 +485,10 @@ func (c *Collector) collectUnitTimeMetrics(conn *dbus.Conn, ch chan<- prometheus
 	if err != nil {
 		return err
 	}
+	err = c.collectUnitTimeMetric(conn, ch, unit, c.unitActiveEnterMonotonicDesc, "ActiveEnterTimestampMonotonic")
+	if err != nil {
+		return err
+	}
 	err = c.collectUnitTimeMetric(conn, ch, unit, c.unitActiveExitTimeDesc, "ActiveExitTimestamp")
 	if err != nil {
 		return err