# Time Series

API Endpoints: [Time Series](/openapi/willow-api#tag/Time-Series)

The Time Series endpoints are used for sending or receiving telemetry data. Once a `Capability` twin has been created that represents the time series, the telemetry associated with that twin can be created using either the twin's dtId (aka twinId) or externalId, a timestamp, and a value. Data is transmitted as an array so time series data can be batched and sent within a single request.

Similarly, time series can be retreived for one or more `Capability` twins at a time using the twinId(s).