If you have a single-entry eVisa, it is valid for 90 days from the arrival date included in your application. If you have a multiple-entry eVisa, it is valid for 1 year from the arrival date included in your application. As long as you can enter Tanzania before the expiry date stated on your eVisa document, you'll be able to visit.
If your eVisa is expired and you’d like to enter Tanzania after the expiry date, or if your travel date is now earlier than the arrival date on your application, you’ll need to apply for another eVisa. Feel free to reach out to us, and we’ll help you figure out your next steps.