Azure performs periodic planned maintenance of SQL Database and managed instance resources. During Azure SQL maintenance events, databases are fully available but can be subject to quick reconfiguration within respective availability SLA's for SQL Database and SQL managed instances.
By default, Azure SQL maintenance policy blocks most impactful updates from 8 AM to 5 PM local time as it allows you to continue working on your business case and have a free hand when it comes to implementing technical decisions. It is meant not only to avoid disruptions during typical peak business hours but also to help you avoid unplanned downtime so that you can leave the office feeling confident about everything going smoothly and move forward with things that need some attention.
Azure allows you to further adjust the maintenance window to a time suitable to Azure SQL resources from the two additional window
Weekday: 10:00 PM to 6:00 AM local time, Monday - Thursday
Weekend: 10:00 PM to 6:00 AM local time, Friday - Sunday
You can follow the article Azure SQL Database Maintenance Window to configure maintenance window using Azure Portal, PowerShell, and Azure CLI.