Authenticate to the QuickBooks Time (TSheets) API using OAuth 2.0 and retrieve employee timesheets

In-depth guide

Steps

1. Register an application in the Intuit Developer Portal to obtain a client ID and client secret for the QuickBooks Time OAuth 2.0 flow.
2. Direct users through the OAuth 2.0 authorization code flow; exchange the authorization code for an access token and refresh token at the Intuit token endpoint.
3. Include the access token as a Bearer token in the Authorization header on all requests to the QuickBooks Time REST API base URL https://rest.tsheets.com/api/v1.
4. GET /timesheets with query parameters such as start_date, end_date, and user_ids to retrieve timesheet records; the API returns a map of timesheet objects keyed by ID.
5. Follow pagination using the more field in the response; when more is true, use the page parameter to retrieve subsequent pages.
6. Refresh the access token before expiry using the refresh token; the QuickBooks Time access token expiry is documented by Intuit and should not be hard-coded.