update the billing date for serverless (#13661)

tidb-cloud/serverless-tier-faqs.md

@@ -21,7 +21,7 @@ Get started with the 5-minute [TiDB Cloud Quick Start](/tidb-cloud/tidb-cloud-qu
 
 ### Is Serverless Tier free during beta?
 
-Until May 30, 2023, Serverless Tier clusters are still free, with a 100% discount off. After that, usage beyond the free quota will be charged. Once the free quota of a cluster is reached, the read and write operations on this cluster will be throttled until you [increase the quota](/tidb-cloud/manage-serverless-spend-limit.md#update-spend-limit) or the usage is reset upon the start of a new month.
+Until May 31, 2023, Serverless Tier clusters are still free, with a 100% discount off. After that, usage beyond the free quota will be charged. Once the free quota of a cluster is reached, the read and write operations on this cluster will be throttled until you [increase the quota](/tidb-cloud/manage-serverless-spend-limit.md#update-spend-limit) or the usage is reset upon the start of a new month.
 
 For more information, see [Serverless Tier usage quota](/tidb-cloud/select-cluster-tier.md#usage-quota).
 

tidb-cloud/tidb-cloud-billing.md

@@ -7,7 +7,7 @@ summary: Learn about TiDB Cloud billing.
 
 > **Note:**
 >
-> [Serverless Tier clusters](/tidb-cloud/select-cluster-tier.md#serverless-tier-beta) are free until May 30, 2023, with a 100% discount off. After that, usage beyond the [free quota](/tidb-cloud/select-cluster-tier.md#usage-quota) will be charged.
+> [Serverless Tier clusters](/tidb-cloud/select-cluster-tier.md#serverless-tier-beta) are free until May 31, 2023, with a 100% discount off. After that, usage beyond the [free quota](/tidb-cloud/select-cluster-tier.md#usage-quota) will be charged.
 
 TiDB Cloud charges according to the resources that you consume. You can visit the following pages to get more information about the pricing.
 

tidb-cloud/tidb-cloud-release-notes.md

@@ -88,7 +88,7 @@ This page lists the release notes of [TiDB Cloud](https://www.pingcap.com/tidb-c
     - Row storage: 5 GiB
     - [Request Units (RUs)](/tidb-cloud/tidb-cloud-glossary.md#request-unit): 50 million RUs per month
 
-  Until May 30, 2023, Serverless Tier clusters are still free, with a 100% discount off. After that, usage beyond the free quota will be charged.
+  Until May 31, 2023, Serverless Tier clusters are still free, with a 100% discount off. After that, usage beyond the free quota will be charged.
 
     You can easily [monitor your cluster usage or increase your usage quota](/tidb-cloud/manage-serverless-spend-limit.md#manage-spend-limit-for-serverless-tier-clusters) in the **Usage This Month** area of your cluster **Overview** page. Once the free quota of a cluster is reached, the read and write operations on this cluster will be throttled until you increase the quota or the usage is reset upon the start of a new month.