diff --git a/rules/manager.go b/rules/manager.go
index f901d8c5694e989bf02af45be10d510fdc5bfce2..2aae53337bdb6238ebc2a1f46b32ec4d29fb78bd 100644
--- a/rules/manager.go
+++ b/rules/manager.go
@@ -385,7 +385,7 @@ func (g *Group) GetEvaluationTimestamp() time.Time {
 
 // setEvaluationTimestamp updates evaluationTimestamp to the timestamp of when the rule group was last evaluated.
 func (g *Group) setEvaluationTimestamp(ts time.Time) {
-	g.metrics.groupLastEvalTime.WithLabelValues(groupKey(g.file, g.name)).Set(float64(ts.Second()))
+	g.metrics.groupLastEvalTime.WithLabelValues(groupKey(g.file, g.name)).Set(float64(ts.UnixNano()) / 1e9)
 
 	g.mtx.Lock()
 	defer g.mtx.Unlock()