> ## 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 |