want to calculate difference hours from dates

[SAS_Learner2]

Hello Friends,

I have data below. When Flag1 = "N" I want to get Date2 populated from Date1 variable of last Flag1 = "Y" record value.

In below data row 2 has Flag1 = "Y", therefore I want this row 2 record date1 (22SEP2021:21:57:00) to be populated retained to Flag1 = "N" records.

Row3 has Flag1 = "N" Hence I want to populate Date3 with Date1 (22SEP2021:21:57:00) of last Flag1 = "Y" record.

row   ID Date1                                 Flag1                Date2
1       001 15SEP2021:15:00:00       N
2       001 22SEP2021:21:57:00       Y
3       001 24SEP2021:21:04:00       N                     22SEP2021:21:57:00

4       001 30SEP2021:21:00:00       Y
5       001 05OCT2021:21:00:00       N                     30SEP2021:21:00:00
6       001 09OCT2021:14:14:00       N                     30SEP2021:21:00:00

Please suggest the approaching way to get this done.

Thank you in advance.

[Kurt_Bremser · Accepted solution]

data want;
set have;
by id;
retain _date2;
format date2 datetime19.;
if first.id then _date2 = .;
if flag = "Y" then _date2 = date1;
if flag = "N" then date2 = _date2;
drop _date2;
run;

[SAS_Learner2]

Great thank you for your quick response.