# text.div
Generated Narrative: CodeSystem time-period-ranges

Language: en

This case-sensitive code system http://terminology.hl7.org/CodeSystem/time-period-ranges defines codes, but no codes are represented here

# publisher
HL7 International Clinical Quality Information Work Group

# description
Defines codes for the representation of time period (e.g. age) ranges that are unambiguous, human readable, and machine-readable as a compositional grammar (i.e. the code system defines rules for constructing codes, rather than explicitly enumerating all possible codes). This CodeSystem profiles [ISO 8601](https://www.iso.org/iso-8601-date-and-time-format.html) for expressing time period ranges through two simple durations (as defined in the [ISO 8601](https://www.iso.org/iso-8601-date-and-time-format.html) specification).

Codes in the code system are defined according to the grammar:

A time period (e.g. age) range is defined as two durations: `[duration1]--[duration2]`, where `duration1` specifies the lower inclusive bound of the age range (everyone who is this age and above) and `duration2` specifies the upper exclusive bound of the age range.

For example, the age range "1-9 years" means everyone who is at least one year old and less than 10 years old represented as `P1Y--P10Y`. The age range "10-14 years" means everyone who is at least 10 years old and less than 15 years old and is represented as `P10Y--P15Y`.

Durations define the amount of time between two time points. These durations are represented in the form `P[n]Y[n]M[n]DT[n]H[n]M[n]S` or `P[n]W`. The `[n]` is replaced by the value for each of the time elements that follow the `[n]` and the letters have the meaning:

* `P` is the duration designator (for period) placed at the start of the duration representation.
	* `Y` is the year designator that follows the value for the number of years.
	* `M` is the month designator that follows the value for the number of months.
	* `W` is the week designator that follows the value for the number of weeks.
	* `D` is the day designator that follows the value for the number of days.
* `T` is the time designator that precedes the time components of the representation.
	* `H` is the hour designator that follows the value for the number of hours.
	* `M` is the minute designator that follows the value for the number of minutes.
	* `S` is the second designator that follows the value for the number of seconds. (Note that seconds can be a decimal in this format to allow for milliseconds)

For example, `P3Y6M4DT12H30M5S` represents a duration of _three years, six months, four days, twelve hours, thirty minutes, and five seconds_.

Date and time elements including their designator may be omitted if their value is zero, and lower-order elements may also be omitted for reduced precision. For example, `P23DT23H` and `P4Y` are both acceptable duration representations. However, at least one element must be present, thus `P` is not a valid representation for a duration of _0 seconds_. `PT0S` or `P0D`, however, are both valid and represent the same duration.

Note that the designator `M` is used for both months and minutes, but this is not ambiguous because the minutes designator must be preceded by the time designator `T`. For example `P1M` is _one month_, while `PT1M` is _one minute_.

Content for this code system is adapted from the definition in the IHE-ADX profile: https://www.ihe.net/uploadedFiles/Documents/QRPH/IHE_QRPH_Suppl_ADX.pdf (Appendix 8K Representation of Age Groups in ADX). In addition, the code system definition is adapted from similar content published as part of the SANER implementation guide. See [Age Range Coding System](https://hl7.org/fhir/uv/saner/CodeSystem-IHE-ADX-agerange.html).

# purpose
This code system is defined to support consistent, unambiguous, human- and machine-readable representations of time period ranges. A primary intended use case is to support the specification of value sets of age ranges for the purposes of data stratification (also referred to as disaggregation).

# copyright
Adapted from content published by IHE Copyright (c) 2015 [IHE International, Inc](http://www.ihe.net/Governance/#Intellectual_Property). Used here according to the terms of the [CC BY 4 License](https://creativecommons.org/licenses/by/4.0/). This CodeSystem constitutes a profile on [ISO 8601](https://www.iso.org/iso-8601-date-and-time-format.html), specifying use of its duration definitions for expressing time period ranges.

# _copyright.extension[].valueString
Rationale: The use of ISO 8601 by particular communities of practice via profiles is encouraged in the specification (older version text posted here [8601-2](https://www.loc.gov/standards/datetime/iso-tc154-wg5_n0039_iso_wd_8601-2_2016-02-16.pdf)) and an example given via [EDTF.](https://en.wikipedia.org/wiki/ISO_8601) There are other prominent, well-used profiles published by other SDOs, including: [RFC 3339 (IETF)](https://www.rfc-editor.org/rfc/rfc3339) and [W3C date and time](https://www.w3.org/TR/NOTE-datetime).