This case-insensitive code system https://fhir.ee/CodeSystem/ee-date-accuracy-indicator defines the following codes:

Code	Display
AAA	Day, month and year are accurate
AAE	Day and month are accurate, year is estimated
AAU	Day and month are accurate, year is unknown
AEA	Day is accurate, month is estimated, year is accurate
AEE	Day is accurate, month and year are estimated
AEU	Day is accurate, month is estimated, year is unknown
AUA	Day is accurate, month is unknown, year is accurate
AUE	Day is accurate, month is unknown, year is estimated
AUU	Day is accurate, month and year are unknown
EAA	Day is estimated, month and year are accurate
EAE	Day is estimated, month is accurate, year is estimated
EAU	Day is estimated, month is accurate, year is unknown
EEA	Day and month are estimated, year is accurate
EEE	Day, month and year are estimated
EEU	Day and month are estimated, year is unknown
EUA	Day is estimated, month is unknown, year is accurate
EUE	Day is estimated, month is unknown, year is estimated
EUU	Day is estimated, month and year are unknown
UAA	Day is unknown, month and year are accurate
UAE	Day is unknown, month is accurate, year is estimated
UAU	Day is unknown, month is accurate, year is unknown
UEA	Day is unknown, month is estimated, year is accurate
UEE	Day is unknown, month and year are estimated
UEU	Day is unknown, month is estimated, year is unknown
UUA	Day and month are unknown, year is accurate
UUE	Day and month are unknown, year is estimated
UUU	Day, month and year are unknown