How do I conevert numeric date variable into consecutive numbers starting at 1

[jspoend]

Hi there, 

I have a dataset with 1 line per ID with one relevant date per ID.

I have transformed the dates into numeric format using 'date_as_num = putn(date,'yymmddn8.');'. 

The date range is 1 January 2018 (i.e. 20180101) to 31 December 2020 (20201231). 

I now need to convert these dates into consecutive numbers starting at 1 with 1 January 2018 being 1, 2 January being 2 and so forth. 

I'm using SAS version 9.4. 

I don't know how to do this. Can anyone help? 

Thank you very much! 

Julia

[Astounding · Accepted solution]

The variable DATE is already on a sliding scale, increasing by 1 every day. To change the scale so it starts at 1 on January 1, 2018, use:

data want;
set have;
sliding_scale = date - '31dec2017'd;;
run;

I would recommend studying up on how SAS handles dates. Time well spent.

[jspoend]

Thank you so much, this worked well. 

I totally agree, that understanding dates in SAS is worthwhile. I