I have done this way.
SAP Provided FM to get seconds CCU_TIMESTAMP_DIFFERENCE.
I used the same Logic and got this result and solved my problem
Thankyou so much.
DATA : v_data_ad(18) TYPE n ,
ls_date TYPE sydatum ,
ls_date1 TYPE sydatum ,
ls_time TYPE sy-uzeit ,
ls_time1 TYPE sy-uzeit.
ls_date = '16010101'.
ls_date1 = '20150618'.
ls_time1 = '210000'.
ls_time = '120000'.
v_data_ad = ( ( ls_date1 - ls_date ) * 86400
+ ( ls_time - ls_time1 ) ) .
v_data_ad = v_data_ad * 10000000 .
Final Result : v_data_Ad = 130790286000000000.