calculate the end_date using start date

[hema_bhure]

Hi,
Thanks In advance

I need to calculate the end_date using start date.

The date columns is in date format.

I want to calculate the end_date on basis of id and term_month_begin and term_month_end.

Pease help me to get data correctly

input dataset
------------------------

id Term_month_begin Term_Month_end Start_dt
1 6 6 2011-01-04
1 12 12 2011-01-04
2 3 3 2011-01-04
2 3 3 2016-02-04
2 6 6 2017-02-03
2 6 6 2018-02-01

output I want
------------------
id Term_month_begin Term_Month_end Start_dt end_dt
1 6 6 2011-01-04 9999-99-99
1 12 12 2011-01-04 9999-99-99
2 3 3 2011-01-04 2016-02-03
2 3 3 2016-02-04 9999-99-99
2 6 6 2017-02-03 2017-12-31
2 6 6 2018-02-01 9999-99-99

[Shmuel]

1) A date like '9999-99-99' is not a valid date. You can either assign value as '9999-12-31' or keep a separate variable for indication (1 or 0);

2) It is not clear when the end_dt should be assigned as '9999-99-99' and when to skip to next following observation(s) or how and when to compute the end_dt. 

[hema_bhure]

hank you Shumuel, but i need to calculate other date apart from 9999-99-99. I have tried lag function but not getting proper output

[PaigeMiller]

But you haven't explained how to determine when you want 9999-99-99.

You also haven't explained how to compute END_DT when it is not 9999-99-99.