original question: What month are under the calendar system of [Vietnamese calendar] ?
answer: month 1
answer type: Month.
auxiliary information: The Vietnamese calendar is a lunisolar calendar that is mostly based on the Chinese calendar. As Vietnam's official calendar is the Gregorian calendar since 1954, the Vietnamese calendar is used mainly to observe lunisolar holidays and commemorations, such as T·∫øt and Mid-Autumn Festival.
[Vietnamese calendar] include what months under its calendar system?