public final void write(Object object) {
        if (object == null) {
            out.writeNull();
            return;
        }

        Class<?> clazz = object.getClass();
        ObjectSerializer writer = getObjectWriter(clazz);

        try {
            writer.write(this, object, null, null, 0);
        } catch (IOException e) {
            throw new JSONException(e.getMessage(), e);
        }
    }
Set global date format pattern in FastJsonConfig

@param dateFormatPattern global date format pattern
src/main/java/com/alibaba/fastjson/serializer/JSONSerializer.java