Why is the Vietnamese and Chinese New Year a day different?

According to scholar Hoang Xuan Han, starting in 1080, the Vietnamese calendar is different from the Chinese calendar due to the difference in how to calculate the calendar and how to round the days of the two countries.

Vietnam and China in 2 different time zones.

During Le Trung Hung period (1533-1789), there were 11 times Vietnam had Tet with China.

By 1967, Vietnam officially followed the GMT +7 time zone, while China followed the GMT +8 time zone. Meanwhile, the start date of the lunar month in international time is calculated from 16 hours onwards.

When calculating the lunar calendar, Vietnam must add 7 hours, while China must add 8 hours.

Every 23 years, the difference in hours accumulates in 1 day. Therefore, some months of the Vietnamese lunar calendar differ by 1 day compared to Chinese, forming a 23-year cycle will have a different Lunar New Year.

Therefore, in 2030 and 2053, Vietnam will eat Tet sooner than China.