Date—accuracy indicator, code AAA

Provision of a date is often a mandatory requirement in data collections.

Most computer systems require a valid date to be recorded in a date field i.e. the month part must be an integer between 1 and 12, the day part must be an integer between 1 and 31 with rules about the months with less than 31 days, and the year part should include the century. Also in many systems, significant dates (e.g. date of birth) are mandatory requirements.

However, in actual practice, the date or date components are often not known (e.g. date of birth, date of injury) but, as stated above, computer systems require a valid date. This means that a date MUST be included and it MUST follow the rules for a valid date. It therefore follows that, while such a date will contain valid values according to the rules for a date, the date is in fact an ‘unknown’ or ‘estimated’ date. For future users of the data it is essential they know that a date is accurate, unknown or estimated and which components of the date are accurate, unknown or estimated.