If you manually set it to Busy, it will revert back to your Outlook calendar status in 24 hours, if you do not change it before then. You can also set your presence to this anytime you want.

Set automatically for you based on your Outlook calendar. Not working and not available to be contacted. (To change these default values, click the Options button, click Status, and then click the arrows next to Show me as Inactive when my status has been idle for this many minutes and Show me as Away when my status has been Inactive for this many minutes.) You can also set your presence to this anytime you want. Skype for Business sets your status to “inactive” when your computer’s been idle for five minutes, and to “away” when your status has been inactive for five minutes. Set automatically for you based on your keyboard activity or Outlook calendar. Logged on but your computer has been idle, or you’ve been away from your computer for a specified (set by you) period of time. You can set your presence to this anytime you want. Stepping away from the computer for a few moments.

You can also set this status when you want others to know you’re in your office even though the computer is idle. Tip: The presence statuses are pre-set in Skype for Business, which means you can’t create a custom status, but you can give your contacts more details about where you are or what you’re doing by adding a personal note.

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