Can I erase GSON Time mark? ex) AM/PM - spring

Question

I use GSON to change the object to json. Also, set and use the code below. As a result, the desired timestamp was obtained.
#Bean
public Gson gson() {
return new GsonBuilder()
.setExclusionStrategies(new AnnotationBasedExclusionStrategy())
.setDateFormat("yyyy-MM-dd HH:mm:ss")
.create();
}
However, there is a mark like AM and PM behind the time.
I hope 13:00:00 to 13:00:00 Not 1:00:00 PM
What should I do to get the results I want? Can existing timestamp results be kept together?
ToString Method shows desired result...
#Entity
#Table(name="tb_work_system")
public class WorkSystem {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(nullable=false)
private String work_system_type;
#Column(nullable=false)
private Time work_start_time;
#Column(nullable=false)
private Time work_end_time;
#Column(nullable=false)
private Time rest_start_time;
#Column(nullable=false)
private Time rest_end_time;
#Column(nullable=false,columnDefinition="BOOLEAN DEFAULT false")
private Boolean deleted=false;
#CreationTimestamp
private Timestamp created_at;
#UpdateTimestamp
private Timestamp updated_at;
}
//ToString Method
WorkSystem [id=1, work_system_type=탄력 근무제, work_start_time=09:00:00, work_end_time=18:00:00, rest_start_time=12:00:00, rest_end_time=13:00:00, deleted=false, created_at=2020-01-31 12:18:13.595343, updated_at=2020-01-31 12:18:13.595343]
//ToJson(Gson)
{"id":1,"work_system_type":"탄력 근무제","work_start_time":"09:00:00 오전","work_end_time":"06:00:00 오후","rest_start_time":"12:00:00 오후","rest_end_time":"01:00:00 오후","deleted":false,"created_at":"2020-01-31 12:18:13","updated_at":"2020-01-31 12:18:13"}