diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Cast.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Cast.java
index 49daba5fc97ec6..0b280af2363192 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Cast.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/Cast.java
@@ -138,6 +138,7 @@ public Expression withConstantArgs(Expression literal) {
 
     @Override
     public boolean isMonotonic(Literal lower, Literal upper) {
+        // Both upward and downward casting of date types satisfy monotonicity.
         if (child().getDataType() instanceof DateLikeType && targetType instanceof DateLikeType) {
             return true;
         }
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/FromSecondMonotonic.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/FromSecondMonotonic.java
index 0b0e319a580888..96dfa7ac6505cd 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/FromSecondMonotonic.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/FromSecondMonotonic.java
@@ -20,7 +20,7 @@
 import org.apache.doris.nereids.trees.expressions.literal.BigIntLiteral;
 import org.apache.doris.nereids.trees.expressions.literal.Literal;
 
-/** monotonicity for from_xx */
+/** monotonicity for from_{xx}second */
 public interface FromSecondMonotonic extends Monotonic {
     @Override
     default boolean isMonotonic(Literal lower, Literal upper) {