Yes, USPS is open on Christmas Eve. They have special hours for that day, typically opening at 8:00am and closing at 2:00pm. If you need to send something by mail, it's important to make sure you have your packages ready to go before the end of the day, as the post office will be closing early. You can also track your packages online to make sure they arrive safely. For more information, you can check the USPS website or call their customer service number.