diff --git a/datetime/src/test/java/tools/jackson/datatype/jsr310/misc/DateTimeSchemasTest.java b/datetime/src/test/java/tools/jackson/datatype/jsr310/misc/DateTimeSchemasTest.java
index 6d118076..654635ab 100644
--- a/datetime/src/test/java/tools/jackson/datatype/jsr310/misc/DateTimeSchemasTest.java
+++ b/datetime/src/test/java/tools/jackson/datatype/jsr310/misc/DateTimeSchemasTest.java
@@ -132,7 +132,11 @@ public void setContext(SerializationContext ctxt) {
         }
     }
 
-    private final ObjectMapper MAPPER = newMapper();
+    // 05-Feb-2025, tatu: Change defaults to Jackson 2.x wrt serialization
+    //    shape (as Timestamps vs Strings)
+    private final ObjectMapper MAPPER = mapperBuilder()
+            .enable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+            .build();
 
     // // // Local date/time types
 
diff --git a/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/InstantSerTest.java b/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/InstantSerTest.java
index 7027e1f0..a542fdc6 100644
--- a/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/InstantSerTest.java
+++ b/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/InstantSerTest.java
@@ -181,7 +181,9 @@ static class Pojo1 {
 
     @Test
     public void testShapeInt() throws Exception {
-        String json1 = newMapper().writeValueAsString(new Pojo1());
+        String json1 = MAPPER.writer()
+                .with(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+                .writeValueAsString(new Pojo1());
         assertEquals("{\"t1\":1651060800000,\"t2\":1651060800.000000000}", json1);
     }
 }
diff --git a/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/LocalDateSerTest.java b/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/LocalDateSerTest.java
index 479d1167..a8326abb 100644
--- a/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/LocalDateSerTest.java
+++ b/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/LocalDateSerTest.java
@@ -130,9 +130,10 @@ public void testSerializationWithTypeInfo01() throws Exception
     @Test
     public void testSerializationWithTypeInfo02() throws Exception
     {
-        ObjectMapper mapper = newMapper();
         final LocalDate localDate = LocalDate.of(2017, 12, 5);
-        String json = mapper.writeValueAsString(new Holder46(localDate, localDate));
+        String json = MAPPER.writer()
+                .with(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+                .writeValueAsString(new Holder46(localDate, localDate));
         assertEquals(a2q("{\"localDate\":[2017,12,5],\"object\":{\"java.time.LocalDate\":[2017,12,5]}}"),
                 json);
     }
diff --git a/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/OffsetDateTimeSerTest.java b/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/OffsetDateTimeSerTest.java
index 65de4a3c..d6abee91 100644
--- a/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/OffsetDateTimeSerTest.java
+++ b/datetime/src/test/java/tools/jackson/datatype/jsr310/ser/OffsetDateTimeSerTest.java
@@ -282,7 +282,9 @@ static class Pojo1 {
 
     @Test
     public void testShapeInt() throws Exception {
-        String json1 = newMapper().writeValueAsString(new Pojo1());
+        String json1 = MAPPER.writer()
+                .with(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+                .writeValueAsString(new Pojo1());
         assertEquals("{\"t1\":1651053600000,\"t2\":1651053600.000000000}", json1);
     }
 }