topic Re: How to know if a date falls between two dates in SAS Programming

How to know if a date falls between two dates

JT99 — Tue, 14 Apr 2020 08:16:31 GMT

Hello
I have a data with two dates, start_date and end_date. If any day in Apr2020 falls between those two dates, then I will create a new variable with value=‘Y’ else value=‘N’. I know it looks easy but I have no idea how to code this.
I’m thinking:
Data want: set have:
If AnyDayInApril2020 between start_date and end_date then value =‘Y’ else value=‘N’; run;
How do I consider the whole month of April into the code? It doesn’t have to be the entire month. As long as a day in Aprl, ex 12Apr2020 is between the two dates then it is valid.

Thanks!

Re: How to know if a date falls between two dates

Jagadishkatam — Tue, 14 Apr 2020 08:29:02 GMT

could you please provide a sample data with expected output to help you

Re: How to know if a date falls between two dates

Kurt_Bremser — Tue, 14 Apr 2020 08:52:54 GMT

The condition would be

if start_date le '30apr2020'd and end_date ge '01apr2020'd

Re: How to know if a date falls between two dates

JT99 — Tue, 14 Apr 2020 09:09:44 GMT

Thank you so much for this solution! I feel bad I never thought of this. Thanks again!

Re: How to know if a date falls between two dates

Kurt_Bremser — Tue, 14 Apr 2020 09:20:35 GMT

It is always good to look at the inverse of a problem; in this case "which individual conditions for the dates would make it impossible for the range to contain a day of April 2020?"

This results in

if start_date gt '30apr2020'd

and

if end_dt lt '01apr2020'd

Since either would invalidate the whole condition, we use "or":

if start_date gt '30apr2020'd or end_dt lt '01apr2020'd

Then we apply some Boolean logic: to invert a compound condition (two conditions connected with AND or OR), you invert the individual parts and convert the logical operator to its opposite; that results in the solution you accepted.