what countries use 24 hour time?

Why use a 24 hour clock?!

Vietnam is one of several Asian countries that make use of the 24-hour clock. Vietnam has used the 24-hour clock since the 19th century, when the French introduced it in their new colony. The 24-hour clock remains in use in Vietnam to the present day, nearly 70 years after Vietnam achieved independence.

12 versus 24 Hour Time: What’s the difference and where does it come from?