Under normal circumstances, the health code needs to be updated every three days in the case of green code, and it can only be extended after at least the health code is boarded in turn within the validity period, otherwise it will be changed to yellow code. However, different regions have different regulations on health codes. Some areas are updated once in a while, and some areas have no time limit and do not need to be updated, as the case may be.
Health code is a personal two-dimensional code based on actual real data, which is generated by citizens or people who have returned to work on their own online declaration and background audit. As an individual entering and leaving electronic certificate locally, the QR code can be declared once, which is universal in the whole city. The introduction of the health code aims to make the work of returning to work more accurate, scientific and orderly.