You can let people know when you are around, set a custom status, and schedule away time in advance.
Open the panel titled Set your availability. Under Your status, choose Available or Away.
Type a short note in "What's your status?" and choose when it clears with "Remove status after...". Options include Don't clear, 30 minutes, 1 hour, 4 hours, Today, This week, and Choose date and time. Use Clear status to remove it.
Use Set to away in advance. Pick From and To dates, add an optional note, and press Add. You can also pull dates in with From time off.
When someone messages you while you are away, they see a banner such as "{name} is away." or "{name} is away until {date}." If you set a custom status, they see "{name} is set to {status}."
When scheduling away time you can turn on Also set me to away in chat, which shows an away banner to anyone who messages you during those dates. Admins can make this automatic with the setting Time off marks users as 'away' in chat. When it is on, adding a time-off period also shows the person as away in chat for those dates, and members can still uncheck it on any single time-off entry.