Is the iPhone's built-in clock accurate? --Why the iPhone can't be heard anymore?

The appeal and strength of the iPhone is that you can understand how to use it without reading the manual. However, there are times when you think you know it but you don't understand it correctly. In this section, we will explain in an easy-to-understand manner "why the iPhone can't be heard anymore". This time, we will answer the question, "Is the iPhone's built-in clock accurate?"

The iPhone has a built-in clock and is used for various functions / apps such as alarms. However, not only the iPhone but also the built-in clock of smartphones / PCs cannot be said to be highly accurate, and errors occur in a short period of time, so the accuracy is maintained by referring to external time information.

iPhone supports the standard "NITZ (Network Identity and Time Zone)" that automatically adjusts the time using a mobile phone line. NITZ is defined by 3GPP (the international technical standard for 3G mobile phone systems), which allows you to keep accurate time anywhere in the world.

However, it was quite difficult to maintain accurate time on the Japanese iPhone until around 2011. That's because Softbank's line, which initially undertook domestic sales of the iPhone, did not support NITZ. If there was an error in the clock, there was no choice but to synchronize it with a computer that has accurate time information, such as by synchronizing it with an NTP server, or adjust it manually.

After that, NITZ was also supported on Softbank lines, and as of 2015, accurate time information can be referenced on all three carriers that handle iPhone. All you have to do is tap "Settings"-> "General"-> "Date and Time" and turn on the "Auto Settings" switch.

However, because NITZ synchronizes via mobile phone lines, it is inferior in terms of "accuracy" in the strict sense of the word when compared to ultra-high precision clocks such as atomic clocks. Please understand that it is "accurate" that is allowed for casual use.