On January 17, 2022, at ~02:06 am UTC, Microsoft communicated via tweet (@MSFT365status) that they were investigating an issue in which users were experiencing Exchange Online mailbox and calendar access issues.
For IT professionals and system admins with Microsoft admin center access, the incident # was EX315207.
Social media responses from the public were mild, with most users making comments as to which geo they were located in and whether or not their access was down.
Within minutes of their initial tweet, Microsoft posted a second message confirming the geo regions impacted: Australia, North America and Japan. Microsoft also stated that they had disabled a recently enabled "flight" in an effort to mitigate impact.
And by 03:51am UTC, it was all over. Microsoft tweeted a final message as to issue # EX315207 and stated that they were confirming availability (all?) had been restored.
A short-lived and minor service interruption it seems, but for any user impacted as well as any IT team responsible for those users, it may not have been a good start to the day.