diff --git a/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/transformation/dag/column/unary/scalar/DateBinFunctionColumnTransformer.java b/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/transformation/dag/column/unary/scalar/DateBinFunctionColumnTransformer.java
index 445ca0560adf4..061543fd16614 100644
--- a/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/transformation/dag/column/unary/scalar/DateBinFunctionColumnTransformer.java
+++ b/iotdb-core/calc-commons/src/main/java/org/apache/iotdb/calc/transformation/dag/column/unary/scalar/DateBinFunctionColumnTransformer.java
@@ -90,19 +90,22 @@ private static LocalDateTime convertToLocalDateTime(long timestamp, ZoneId zoneI
   }
 
   private static long convertToTimestamp(LocalDateTime dateTime, ZoneId zoneId) {
-    // Converting LocalDateTime to Seconds since epoch
-    long epochMilliSecond = dateTime.atZone(zoneId).toInstant().toEpochMilli();
-    // Get the nanoseconds section
-    long nanoAdjustment = dateTime.getNano();
+    // Encode from the epoch second and the nanosecond-of-second. toEpochMilli() already
+    // contains the whole milliseconds of that second, so adding getNano() on top counts
+    // those milliseconds a second time.
+    Instant instant = dateTime.atZone(zoneId).toInstant();
+    long seconds = instant.getEpochSecond();
+    long nanoOfSecond = instant.getNano();
 
     switch (CommonDescriptor.getInstance().getConfig().getTimestampPrecision()) {
       case "ms":
-        return epochMilliSecond + nanoAdjustment / NANOSECONDS_IN_MILLISECOND;
+        return Math.addExact(
+            Math.multiplyExact(seconds, 1000L), nanoOfSecond / NANOSECONDS_IN_MILLISECOND);
       case "us":
-        return TimeUnit.MILLISECONDS.toMicros(epochMilliSecond)
-            + nanoAdjustment / NANOSECONDS_IN_MICROSECOND;
+        return Math.addExact(
+            Math.multiplyExact(seconds, 1_000_000L), nanoOfSecond / NANOSECONDS_IN_MICROSECOND);
       case "ns":
-        return TimeUnit.MILLISECONDS.toNanos(epochMilliSecond) + nanoAdjustment;
+        return Math.addExact(Math.multiplyExact(seconds, 1_000_000_000L), nanoOfSecond);
       default:
         throw new IllegalArgumentException(
             CalcMessages.EXCEPTION_UNKNOWN_PRECISION_0119BEB0
diff --git a/iotdb-core/datanode/src/test/java/org/apache/iotdb/db/queryengine/transformation/dag/column/unary/scalar/DateBinFunctionTest.java b/iotdb-core/datanode/src/test/java/org/apache/iotdb/db/queryengine/transformation/dag/column/unary/scalar/DateBinFunctionTest.java
index 013e8c8429081..1c222623c7720 100644
--- a/iotdb-core/datanode/src/test/java/org/apache/iotdb/db/queryengine/transformation/dag/column/unary/scalar/DateBinFunctionTest.java
+++ b/iotdb-core/datanode/src/test/java/org/apache/iotdb/db/queryengine/transformation/dag/column/unary/scalar/DateBinFunctionTest.java
@@ -19,6 +19,10 @@
 
 package org.apache.iotdb.db.queryengine.transformation.dag.column.unary.scalar;
 
+import org.apache.iotdb.calc.transformation.dag.column.leaf.NullColumnTransformer;
+import org.apache.iotdb.calc.transformation.dag.column.unary.scalar.DateBinFunctionColumnTransformer;
+import org.apache.iotdb.commons.conf.CommonDescriptor;
+
 import org.junit.Before;
 import org.junit.Test;
 
@@ -28,6 +32,9 @@
 import java.util.TimeZone;
 
 import static org.apache.iotdb.calc.transformation.dag.column.unary.scalar.DateBinFunctionColumnTransformer.dateBin;
+import static org.apache.iotdb.calc.transformation.dag.column.unary.scalar.DateBinFunctionColumnTransformer.nextDateBin;
+import static org.apache.tsfile.read.common.type.TimestampType.TIMESTAMP;
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 
 public class DateBinFunctionTest {
@@ -126,4 +133,53 @@ public void testSourceBeforeUnixEpoch() throws ParseException {
             zoneId);
     assertEquals(getTimestamp("1969-12-31 00:00:00.000"), result);
   }
+
+  @Test
+  public void testMonthBinKeepsFractionalOrigin() throws ParseException {
+    long origin = 500L;
+    long oneMonthLater = getTimestamp("1970-02-01 00:00:00.500");
+    long justBeforeNextMonth = oneMonthLater - 1;
+
+    assertEquals(origin, dateBin(origin, origin, 1, 0, zoneId));
+    assertEquals(origin, dateBin(justBeforeNextMonth, origin, 1, 0, zoneId));
+    assertEquals(oneMonthLater, dateBin(oneMonthLater, origin, 1, 0, zoneId));
+
+    long marchOrigin = getTimestamp("2024-03-15 00:00:00.500");
+    long aprilOrigin = getTimestamp("2024-04-15 00:00:00.500");
+    assertEquals(marchOrigin, dateBin(marchOrigin, marchOrigin, 1, 0, zoneId));
+    assertEquals(aprilOrigin, dateBin(aprilOrigin, marchOrigin, 1, 0, zoneId));
+
+    long exactSecond = getTimestamp("2024-03-15 00:00:00.000");
+    long nextExactMonth = getTimestamp("2024-04-15 00:00:00.000");
+    assertEquals(exactSecond, dateBin(exactSecond, exactSecond, 1, 0, zoneId));
+    assertEquals(nextExactMonth, dateBin(nextExactMonth, exactSecond, 1, 0, zoneId));
+  }
+
+  @Test
+  public void testMonthBinStartEndAndGapFillKeepFractionalMillis() throws ParseException {
+    long origin = 500L;
+    DateBinFunctionColumnTransformer transformer =
+        new DateBinFunctionColumnTransformer(
+            TIMESTAMP, 1, 0, new NullColumnTransformer(), origin, zoneId);
+
+    long oneMonthLater = getTimestamp("1970-02-01 00:00:00.500");
+    assertArrayEquals(new long[] {origin, oneMonthLater}, transformer.dateBinStartEnd(origin));
+    assertEquals(oneMonthLater, nextDateBin(1, zoneId, origin));
+  }
+
+  @Test
+  public void testMonthBinKeepsSubMillisecondOriginUnderUsAndNs() {
+    String originalPrecision = CommonDescriptor.getInstance().getConfig().getTimestampPrecision();
+    try {
+      // 1.5 ms after the epoch, expressed in microseconds and nanoseconds.
+      CommonDescriptor.getInstance().getConfig().setTimestampPrecision("us");
+      assertEquals(1500L, dateBin(1500L, 1500L, 1, 0, zoneId));
+      assertEquals(1500L, nextDateBin(1, zoneId, 1500L) - 2678400000000L);
+
+      CommonDescriptor.getInstance().getConfig().setTimestampPrecision("ns");
+      assertEquals(1_500_000L, dateBin(1_500_000L, 1_500_000L, 1, 0, zoneId));
+    } finally {
+      CommonDescriptor.getInstance().getConfig().setTimestampPrecision(originalPrecision);
+    }
+  }
 }