The company is taking July 3rd as a holiday. That is in the middle of
the sprint. How do I set that day as a holiday for everyone so it is
not allocatable on the sprint planning?

Unfortunately, it is currently not possible to add out of office entries
for everyone - each developer has to do it on his own (alternatively, a
user with ADMIN privileges could add the entry manually for everyone)

If you are interested, you can subscribe yourself / comment on the
following related work items:

https://jazz.net/jazz/resource/itemName/com.ibm.team.workitem.WorkItem/39772
https://jazz.net/jazz/resource/itemName/com.ibm.team.workitem.WorkItem/31910

Thanks!

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MikeS
Jazz Agile Planning team