How can I Add Days to a date property in Cypher? - date

Question

I have been working on a readmission issue using a clinical graph dataset. Let's say a patient is being readmitted within 30 days. So, this means I need add 30 days to the first date (visit date) for the second visit date.
Here is the Cypher query:
MATCH(p:Person)-[r:PATIENT_HAS]->(e:Encounter)
WITH p,e
MATCH (p)-[r:PATIENT_HAS]-(e2:Encounter) WHERE e2.ADMIT_DATE < (e.ADMIT_DATE + 30)
This query won't work because the date property is in YYYYMMDD format. For example, if it is 20151225, it will give 20151255. But I need to get it as 20160124 after adding 30 days. Is there any other way to use a different format than YYYYMMDD. I know that there is string format as YYYY-MM-DD, but what is the way to use this format for adding days?
How can accomplish this?
I would appreciate your help.

Answer 1

The best way to deal with dates in Neo4j in my opinion is to have them saved as UNIX epoch time in miliseconds or seconds. We have a great plugin in Neo4j called apoc procedures that allows you to use awesome procedures. In your specific case I would utilize apoc.date.*procedures and parse your date format to epoch time in seconds.
MATCH (e:Encounter)
WITH e,apoc.date.parse(e.ADMIT_DATE,"s","YYYYMMDD") as unix
set e.unix = unix
So now your query would look like :
MATCH(p:Person)-[r:PATIENT_HAS]->(e:Encounter)
MATCH (p)-[r:PATIENT_HAS]-(e2:Encounter)
WHERE e2.unix < e.unix + (30 * 24 * 60 * 60)
Ofcourse you can simplify this query and make it shorter:
MATCH (e2:Encounter)-[r:PATIENT_HAS]-(p:Person)-[r:PATIENT_HAS]->(e:Encounter)
WHERE e2.unix < e.unix + (30 * 24 * 60 * 60)

Answer 2

You can construct a Duration, and add it directly to a date.
Here is an example in Cypher:
RETURN Date() + Duration({days: 30})
Reference: https://neo4j.com/docs/cypher-manual/current/functions/temporal/duration/

Answer 3

I'm currently using Neo4j 4.0.3 and the following works:
RETURN REPLACE(toString(date('20151225') + duration('P30D')),'-','')
// "20160124"

Answer 4

We found out a temporary solution: We are setting a specific date in the past (1/1/2009 in our case), and are getting the difference between the first visit (e.ADMIT_DATE-1/1/2009) and the second visit (e2.ADMIT_DATE-1/1/2009) as days. Then we are able to get the difference between the first and second visits (e2.DAYS-e.DAYS) to figure out 30 days for the readmission criteria.
I had checked out the apoc procedures plugin and it seemed a bit complicated. But I can definitely retry it. Many thanks for your great responses folks.