Ask HN: are there laws around employees knowing if/why a coworker has time off?

It appears that there are no laws at all in the US about vacation or sick day privacy, but your state may have some. A search for vacation privacy law and similar terms yielded the articles below. There appears to be some evidence that employees have no right to ask you what specifically you are doing on your PTO days, but I didn't find any evidence that prohibited employers from disclosing that you took a sick or vacation day to other employees. HIPAA might apply if for example you provided a doctor's note to HR that explained that you were getting a particular procedure done, and they put that info on the shared calendar. If that is a concern, you should just not share specifics. Just say "I'm requesting a sick day" or "I'm requesting a vacation day" and refuse to elaborate.

http://money.usnews.com/money/blogs/outside-voices-careers/2...

http://www.nolo.com/legal-encyclopedia/monitoring-employees-...

Try "employee health privacy". Regardless of legality, I don't know why an employer would even want to have a common/shared calendar that includes a history of sick days off. Of course, a manager would maintain that or have access to a system that maintains that, but I don't know why everyone else in the workgroup needs access to a history - even an unofficial one - of someone else's sick days off. I'm sure some will keep unofficial track, especially if the co-worker's absence impacts them - or they perceive that it does - but for the manager to purposely do that. . .I don't see the point.

[IANAL]

The bigger can of worms for employers in regard to employee health status is ADA. It often encourages sophisticated employers to avoid the concept of sick days altogether and just lump everything into one type of leave.