Hello everyone

I am trying to get the difference between two dates to calculate follow up per patient
I am using a long format dataset with various observations per patient id, no missing values.

I can't spot why for some patients I get 01/01/2500 as the maxdate date, which is wrong.


edate format is float %dM_d,_CY , is this an issue?

This is what I'm using:

bysort patid : egen maxdate = max(edate)

Does anyone know why this might be happening?

Thank you,

Louisa