Sounds like you want these features:
During the day the Auto Attendant would answer incoming calls either immediately or after 3 or 4 rings as a backup and give a Greeting and menu that reflects that you are open for business and proper directions for dialing etc. Any incoming caller reaching an extensions mailbox would hear that persons day greeting automatically.
When it is time to close either at the std time or early and you wish to press 1 button to put system in night mode, this action would immediately change the greeting and instructions menu heard by incoming callers to your Night Greeting and instructions and also mean any caller reaching a personal mailbox would hear that persons after hours Greeting, all with no action from anyone but just Pressing the Night button.
You might wish to have Holiday greeting and menu that can be activated by pressing 1 button, or a lunch greeting and menu by pressing 1 button. Or you may wish to have all of the above controlled by a time schedule, Holidays being scheduled up to 1 year in advance.
If this is what you want you may have to look to a higher line NEC system with more robust AA and voice mail or other system.
If you don't need these advanced functions,
the DSX will work great for you. (IMHO)
It's hard to beat for the investment vs features in it's market.
But as others have suggested, get with a local dealer, and have it set up properly. I'm sure any would be happy to show you how to admin the system
if you wish to do so.

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