diff --git a/core/src/main/java/org/apache/calcite/rex/RexInterpreter.java b/core/src/main/java/org/apache/calcite/rex/RexInterpreter.java
index 549efa5387f..4922c2ab73d 100644
--- a/core/src/main/java/org/apache/calcite/rex/RexInterpreter.java
+++ b/core/src/main/java/org/apache/calcite/rex/RexInterpreter.java
@@ -379,6 +379,7 @@ private static Comparable ceil(RexCall call, List<Comparable> values) {
     switch (unit) {
     case YEAR:
     case MONTH:
+    case WEEK:
       switch (call.getKind()) {
       case FLOOR:
         return DateTimeUtils.unixTimestampFloor(unit, v);
@@ -403,7 +404,7 @@ private static TimeUnitRange subUnit(TimeUnitRange unit) {
     case QUARTER:
       return TimeUnitRange.MONTH;
     default:
-      return TimeUnitRange.DAY;
+      return unit;
     }
   }
 
diff --git a/core/src/main/java/org/apache/calcite/rex/RexSimplify.java b/core/src/main/java/org/apache/calcite/rex/RexSimplify.java
index 3b0b04043b5..1ecb15d62b0 100644
--- a/core/src/main/java/org/apache/calcite/rex/RexSimplify.java
+++ b/core/src/main/java/org/apache/calcite/rex/RexSimplify.java
@@ -2652,6 +2652,7 @@ private static boolean canRollUp(TimeUnit outer, TimeUnit inner) {
     switch (outer) {
     case YEAR:
     case MONTH:
+    case WEEK:
     case DAY:
     case HOUR:
     case MINUTE:
@@ -2662,6 +2663,7 @@ private static boolean canRollUp(TimeUnit outer, TimeUnit inner) {
       case YEAR:
       case QUARTER:
       case MONTH:
+      case WEEK:
       case DAY:
       case HOUR:
       case MINUTE:
@@ -2671,6 +2673,12 @@ private static boolean canRollUp(TimeUnit outer, TimeUnit inner) {
         if (inner == TimeUnit.QUARTER) {
           return outer == TimeUnit.YEAR;
         }
+        if (outer == TimeUnit.WEEK && inner != TimeUnit.YEAR && inner != TimeUnit.MONTH) {
+          return true;
+        }
+        if (inner == TimeUnit.WEEK && outer != TimeUnit.YEAR && outer != TimeUnit.MONTH) {
+          return false;
+        }
         return outer.ordinal() <= inner.ordinal();
       default:
         break;
diff --git a/core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java b/core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java
index 042dcae1f0a..0b550e5b958 100644
--- a/core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java
+++ b/core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java
@@ -483,13 +483,18 @@ public class RexImplicationCheckerTest {
         hasToString("TRIM('BOTH', 'a', '1111':VARCHAR)"));
   }
 
-  /** Test case for simplifier of ceil/floor. */
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-2178">[CALCITE-2178]
+   * Extend expression simplifier to work on datetime CEIL/FLOOR functions</a>,
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-7304">[CALCITE-7304]
+   * Floor/Ceil can not simplify with WEEK TimeUnit</a>. */
   @Test void testSimplifyCeilFloor() {
     // We can add more time units here once they are supported in
     // RexInterpreter, e.g., TimeUnitRange.HOUR, TimeUnitRange.MINUTE,
     // TimeUnitRange.SECOND.
     final ImmutableList<TimeUnitRange> timeUnitRanges =
-        ImmutableList.of(TimeUnitRange.YEAR, TimeUnitRange.MONTH);
+        ImmutableList.of(TimeUnitRange.YEAR, TimeUnitRange.MONTH, TimeUnitRange.WEEK,
+            TimeUnitRange.HOUR, TimeUnitRange.MINUTE, TimeUnitRange.SECOND);
     final Fixture f = new Fixture();
 
     final RexNode literalTs =