An urgent service quoted in hours is quoted in Vietnamese office hours. Applying at 9pm in London is not the same as applying at 9am in Hanoi.
The reference timezone
Vietnam runs on GMT+7 with no daylight saving. From London that is seven hours ahead in winter and six in summer; from New York, twelve and eleven; from Sydney, three behind.
What this means in practice
A four-hour service submitted at midday in New York arrives in Hanoi in the middle of the night. The clock effectively starts when the office opens the next morning.
Plan your submission window
If you need genuine same-day handling, submit during Vietnamese business hours. For travellers in the Americas, that means late evening or overnight local time.
Public holidays
Tet, Reunification Day and National Day close offices for several consecutive days. Around these periods, add a comfortable margin regardless of the tier you pay for.