Under normal circumstances, the health code needs to be updated every three days in the case of green code. At least the health code can be delayed in turn during 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.
In either case, we should actively rely on the health code to travel and ensure the health of ourselves and others.