The United States Postal Service (USPS) will not deliver mail on Presidents' Day 2018 (January 19), according to their official website. President's Day is a federal holiday, so all federal offices are closed. However, the USPS will still deliver Amazon packages on Sunday, before the holiday. All Post Offices will reopen on Tuesday, February 20, 2018.
The good news: UPS and FedEx will still deliver on Presidents' Day. This means you should still receive packages from UPS and FedEx on time. You can find the complete list of holidays for 2018 on the UPS and FedEx websites.