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Date of birth data mandated standard

Date of birth data standard [PDF 286 KB]


Purpose of mandated standard

The purpose of this standard is to mandate 'ISO 8601 - 1:2019, Date and time — representations for information interchange — part 1: basic rules', to be used to format date of birth for sharing purposes.

This mandated standard applies to data being shared between organisations.

This mandated standard does not mandate the collection or storage of date of birth. These may vary depending on the needs of the organisation.

ISO 8601 - 1:2019 Date and time — representations for information interchange — part 1: basic rules


Date of birth is the localised year, month, and day a natural person was born.


The minimum required format for compliance when sharing date of birth information is YYYY-MM-DD (or YYYYMMDD).

Further information

ISO 8601 Date representation and format examples:

  • ‘2018-08-01’ is a date and time expression that indicates the first day of August of 2018 in the Gregorian calendar.
  • [date] is a date and time representation that can be expanded as [year][month][day], which itself can be expanded into [YYYY][MM][DD]; ‘20180801’ is a date and time expression that conforms to this representation.

While this standard does not mandate how date of birth data is collected or stored in databases, guidance on the collection of date of birth can be found in the 'Statistical standard for age'.

Statistical standard for age


Localised date

The date at the location of birth is to be used and not adjusted for any time zone offsets.

Absence of data of birth

When a date of birth is not recorded a default date should not be used to indicate this. Instead do not supply any date.


The mandated standard does not require date of birth to be verified, but if it is this may be useful information to be noted when shared.

Document management

Document ID: DCS-002-00

Document version: 1.0

Approval date: 12/12/2019

Effective date: 02/04/2020

Review date: 02/04/2021

Attribution and use

This document was created by a cross public sector working group which was led by Stats NZ. For more information please contact

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Content last reviewed 14 February 2022.