docs(source-facebook-marketing): document timezone handling for Insights streams (#74013)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: devin-ai-integration[bot]

docs/integrations/sources/facebook-marketing.md

@@ -279,7 +279,7 @@ The Facebook Marketing source connector supports the following [sync modes](http
 **Notes on Streams:**
 
 :::info Custom Audiences
-The `rule` field in the `Custom Audiences` stream may not be synced for all records due to limitations with the Facebook Marketing API. Syncing this field may also cause your sync to return the error message `Please reduce the amount of data` See our Troubleshooting section for more information.
+The `rule` field in the `Custom Audiences` stream may not be synced for all records due to limitations with the Facebook Marketing API. Syncing this field may also cause your sync to return the error message `Please reduce the amount of data`. See our Troubleshooting section for more information.
 :::
 
 Airbyte also supports the following Prebuilt Facebook Ad Insights Reports:
@@ -339,6 +339,12 @@ Built-in Ads Insights streams and Prebuilt Ads Insights Reports use `level=ad` b
 
 <EntityRelationshipDiagram></EntityRelationshipDiagram>
 
+## Timezone handling for Insights streams
+
+The Facebook Insights API interprets `time_range` date filters (`since` and `until`) in the ad account's timezone, not UTC. For ad accounts in timezones ahead of UTC (such as `Asia/Tokyo` at UTC+9 or `Europe/Berlin` at UTC+1), the connector automatically detects each account's timezone and adjusts the sync date range so that the current day's data is not missed. This per-account adjustment applies to all Ads Insights streams, including built-in and custom Insights streams. No configuration is required.
+
+If you sync multiple ad accounts in different timezones within a single connection, each account's date range is computed independently based on its own timezone setting.
+
 ## Facebook Marketing Attribution Reporting
 
 The Facebook Marketing connector uses the `lookback_window` parameter to repeatedly read data from the last `<lookback_window>` days during an Incremental sync. This means some data will be synced twice (or possibly more often) despite the cursor value being up to date, in order to capture updated ads conversion data from Facebook. You can change this date window by adjusting the `lookback_window` parameter when setting up the source, up to a maximum of 28 days. Smaller values will result in fewer duplicates, while larger values provide more accurate results. For a deeper understanding of the purpose and role of the attribution window, refer to this [Meta article](https://www.facebook.com/business/help/458681590974355?id=768381033531365).