Manisha, One small logic you need to learn then you can do whatever you want regarding date.
Data : lv_date type dats,
lv_month type char2,
lv_day type char2,
lv_year type char4.
lv_date = sy_datum. "today's date. (20131127)
lv_day = lv_date+6(2).
lv_month = lv_date+4(2).
lv_year = lv_date+0(4).
"Now Concatenate all these day month and year in required format. and if you want to subtract something then perform that and concatenate.
concatenate lv_day lv_month lv_year into lv_new_date saprated by '/'. " 27/11/2013