Without knowing exactly how you are tracking time within your project it is difficult to offer a solution to show how to use that time to determine when something is open or closed.
Generally you would use one or more varaibles to track the current state of something, and then use an <<if>> macro to determine is a link allowing access to the coffee shop should be shown or not.
basic example: If you had two variables named $hour and $minute and if those variables were currenly equal to 8 and 30
<<set $hour to 8>>
<<set $minute to 30>>
... then you could use a condition like the following to determine if the current time is later than the start of the open period.
<<set _time to ($hours * 60) + $minutes>>
<<if _time gte 510>>[[Enter the Coffee Shop|Coffee Shop]]<</if>>
note: 8:30am is 510 minutes after midnight.
You would next extend the above condition to also determine if the current time is earlier than the end of the open period.
<<if _time gte 510 and _time lt 1140>>[[Enter the Coffee Shop|Coffee Shop]]<</if>>
note: 7:00pm is 1140 minutes after midnight.
You could further extend the about condition to show a 'closed' message when the current time is outside the open period.
<<if _time gte 510 and _time lt 1140>>[[Enter the Coffee Shop|Coffee Shop]]\
<<else>>Coffee Shop Closed<</if>>