---
schema_version: "1"
id: 0e6617fc71d74a75cfc0eda24a62d7dcc5902001a2cd109dfedae230c729dee1
title: Check External Calendars to Determine Resource Availability
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/platform/264-0-0/ls_read_external_calendar.md
canonical_url: https://help.salesforce.com/s/articleView?id=platform.ls_read_external_calendar.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: ed199da6013a477c007c4d05a8c79dabc14118ad33544a81c34e01affa8aa4a1
description: When you run a Salesforce Scheduler flow or make an API call, the Apex interface makes a synchronous call to the Apex class. The Apex interface passes the details of the requested service resources and timelines for which Salesforce Scheduler wants to find the resources’ availability on the external calendar. The Apex class checks the external calendar events and returns the time slots where resources aren’t available. Salesforce Scheduler excludes the unavailable time slots during appointment scheduling.
products:
  - Scheduler
  - Salesforce Platform
release: "264"
---
# Check External Calendars to Determine Resource Availability

When you run a Salesforce Scheduler flow or make an API call, the Apex interface makes a synchronous call to the Apex class. The Apex interface passes the details of the requested service resources and timelines for which Salesforce Scheduler wants to find the resources’ availability on the external calendar. The Apex class checks the external calendar events and returns the time slots where resources aren’t available. Salesforce Scheduler excludes the unavailable time slots during appointment scheduling.

### Required Editions

<table class="slds-table slds-table_bordered slds-max-medium-table_stacked slds-m-bottom_small edition"><colgroup><col></colgroup><tbody><tr class=""><td class="slds-cell-wrap" style="vertical-align:top;">Available in: Lightning Experience.</td></tr><tr class=""><td class="slds-cell-wrap" style="vertical-align:top;">Available in: <strong>Enterprise</strong> and <strong>Unlimited</strong> Editions</td></tr></tbody></table>

![External calendar update overview](https://sf-zdocs-cdn-prod.zoominsoftware.com/tdta-platform-scheduler-264-0-0-production-enus/0530be2f-891f-4263-a0d7-96ddca56a717/scheduler/images/ls_read_ext_cal_events.png)

1. From Setup, in the Quick Find box, enter Scheduling Policies, then select **Scheduling Policies**.
2. Click **Edit** next to Default Appointment Scheduling Policy or your custom scheduling policy.
3. Click in the Check External Systems for Resource Availability field, and select your Apex class.
4. Save your changes.

#### See Also

- [_Apex Developer Guide_: LxScheduler Namespace](https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_namespace_lxscheduler.htm)