Look under the date in the dashboard header. Depending on the history you will see one of:

• "This day was automatically closed on <date/time>." – the Cut-off Timer closed it.
• "This day was manually closed by <user> on <date/time>." – someone clicked Close Meal Selections.
• "This day was automatically closed on … and later manually closed by <user> on …." – it was auto-closed, reopened, then closed again by hand.
• A red "The system closed this day automatically on … and you reopened it. You will need to manually close this day." – it is currently open after an automatic close.

All open/close/finish changes are also written to the admin activity log.