The validity of the E-Visa is 30 days (single entry). The validity period of your E-Visa begins from the date specified in your approved e-Visa document. You can enter Vietnam on any date within this validity period.

Therefore, you cannot enter Vietnam before that entry day/ before or after the validity period specified in your e-Visa. you must apply for the new E-Visa.

But you can enter after the entry date specified in your E-Visa within this validity period.