How to get end of business day date and time based on appian process calendar

AFAIK there is no function to get the data saved in a process calendar.  If you want to retrieve the value and then compare against something/ store somewhere then that part is not possible.

If you need to apply some conditions based on it, the below functions can be used to create evaluation expressions and have the system perform the checks. 

• a!addDateTime()
• a!subtractDateTime()
• calisworkday()
• calisworktime()
• calworkdays()
• calworkhours() 

E.g. if you want a process to run only within the work hours added in calendar then in condition you can use the below expression and process will not trigger outside business hours.

calisworktime(now(),calendar_name)

Let me know if you are looking for a specific scenario otherwise hope this helps!