> ## Documentation Index
> Fetch the complete documentation index at: https://docs.metriport.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Period

> Base StructureDefinition for Period Type: A time period defined by a start and end date and optionally time.

## Properties

| Name | Required | Type | Description |
| - | - | - | - |
| id | No | string | Unique id for inter-element referencing |
| extension | No | [Extension](/medical-api/fhir/data-types/extension)\[] | Additional content defined by implementations |
| start | No | dateTime | Starting time with inclusive boundary |
| end | No | dateTime | End time with inclusive boundary, if not ongoing |


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