Insert command generates error in MySQL

I was given the following code to create some tables in MySQL:

create table vt_staff (
    stf_id          decimal(6,0)   primary key
  , stf_name_last   varchar(25)    not null
  , stf_name_first  varchar(25)    not null
  , stf_job_title   varchar(25)    not null
  , constraint stf_id_range         check (stf_id > 0)
  , constraint job_title_values
         check ( stf_job_title in ('vet', 'vet assnt', 'clerical', 'kennel'))
);

create table vt_animals(
    an_id           decimal(6,0)  primary key
  , an_type         varchar(25)    not null  
  , an_name         varchar(25)    null
  , an_dob          date            not null
  , cl_id           decimal(6,0)     not null  
  ,  constraint an_id_range         check (an_id > 0)
  ,  constraint an_dob_ck           check (trunc(an_dob) = an_dob)
  );

create table vt_exam_headers(
    ex_id           decimal(6,0)     primary key
  , an_id           decimal(6,0)     not null  
  , stf_id          decimal(6,0)     not null  
  , ex_date         date            not null
  , constraint vt_exam_headers_animal_fk  foreign key(an_id) references vt_animals
  , constraint vt_exam_headers_staff_fk   foreign key(stf_id) references vt_staff
  , constraint ex_id_range          check (ex_id > 0)
  , constraint exam_date_range      check (ex_date >= date '2010-01-01')
  );

All the code executed fine. However when I tried running the following insert statements for the vt_exam_headers table, I keep obtaining an error, e.g..,

insert into vt_exam_headers(ex_id, an_id, stf_id, ex_date)
  values (2289, 21320, 38, TO_DATE('2015-04-11 13:00', 'YYYY-MM-DD HH24:MI') );

insert into vt_exam_headers(ex_id, an_id, stf_id, ex_date)
  values (2290, 21320, 38, TO_DATE('2015-04-11 17:00', 'YYYY-MM-DD HH24:MI') );
 
I believe the problem is related to the TO_DATE function, but am not sure of the correct syntax.

Would appreciate any help.