Yes, smartphones are not Android / iPhone, and basically do not require time adjustment. If the SIM card of the contracted carrier is inserted and connected to the mobile line, the time will continue to be accurate. You only need to carry it as a smartphone, and there is no so-called "clock mess".
This is because most of the smartphones currently available support "NITZ (Network Identity and Time Zone)". NITZ is a standard that provides information such as current time and time zone via base stations, and is provided by communication carriers. If you are connected to the line of a communication carrier that provides NITZ, the time is adjusted periodically, so there is no need for maintenance. In the past, there was a difference in the presence or absence of the corresponding by communication carriers, because it provides all of 2019, the current Japan three major carriers, and corresponds to which access is also NITZ including the MVNO.
To set the time using NITZ, go to “Settings” → “System” → “Date and Time” and “Automatic Date and Time” switch in Android OS, and on iOS “Settings” → “General” → “Date and Time”. Activate a certain "automatic setting" switch to enable it. If the switch is turned off, the time information provided by NITZ will not be referenced, and the current time will shift after a while.
The NITZ standard stipulates that the time difference between the Coordinated Universal Time (UTC) and the base station equipment should be kept to 1.5 microseconds or less. If the smallest unit of time handled on a daily basis is "seconds" for the general public, it is much more accurate, but it is not as accurate as an atomic clock in femtoseconds (10 minus 15th seconds).