How to handle notes from patients older than 90 years?

Patients older than 90 years are protected by HIPAA. In general, Philter shifts dates and leaves in ages. For the group patients that are older than 90 years at the time of notes publication the following approach is implemented:

We need to adjust the date of birth so that patients appear to be 90 years old and obscure all ages found in the text to match the new DOB.

Let dob_orig, dod_orig, age_string be the patient’s identified date-of-birth, date-of-death and age found in the text, respectively, date_orig be an identified event date in the text, and year[ x ] be a floor function returning the integer year of x, then

dob_shifted = dob_orig – date_offset
dod_shifted = dod_orig – date_offset
date_shifted = date_orig – date_offset
dod_deid = dod_shifted
date_deid = date_shifted
reference = {dod_shifted if exists, today otherwise}
91birthdate_shifted = dob_shifted + 91 years
current_age_shifted = reference - dob_shifted

If current_age_shifted < 91:
    dob_deid = dob_shifted
    age_deid = age_string
else (i.e. the patient is older than 90):
    ninety_shift = year[ current_age_shifted ] – 90
    dob_deid = dob_shifted + ninety_shift
    age_deid = "*****"

date_deid = max[ date_deid, dob_deid ]