difference between date mysql code example

Example 1: mysql date between two dates

ex1:
SELECT * FROM `objects` 
WHERE  (date_field BETWEEN '2010-01-30 14:15:55' AND '2010-09-29 10:15:55')

ex2:
WHERE 
   requireddate BETWEEN 
     CAST('2003-01-01' AS DATE) AND 
     CAST('2003-01-31' AS DATE);

Example 2: date between in mysql

SELECT * FROM `objects` 
WHERE  (date_field BETWEEN '2010-01-30 14:15:55' AND '2010-09-29 10:15:55')