That uses the cell phone as a clock depends on the time of the unit to be right. Some people prefer to even keep the watch of the mobile phone in advance a few minutes to always have that feeling that you are late when in fact is at the time. It is a practice that is interesting, but can become complicated to keep if the clock of the mobile phone is not reliable. Nowadays it is possible to configure the phone to set the clock with the carrier, but such practice does not always work well and is not very reliable on all devices and carriers.
If you have an Android phone there is a way more guaranteed to keep the clock of your mobile phone to always be right. Computers and servers all over the world use what is called NTP (Network Time Protocol) which is a service of watch online. Any computer can access and “ask the question” what is the time here where I am? The NTP responds, and the computer hits getting synchronized.
For Android, is there an app super configurable to do the same thing: keep the clock always right. It needs that you have an Android “rooteado” and connection to the internet once in a while for it to update. You can configure the frequency of update and the server with which you want to update. I chose the same that I put in the Windows and that I put on all the computers that I use, even Linux. The NTP server I used was time.windows.com .
The android application to synchronize the clock, ClockSync. It is as well complete, free, and has dozens of settings options. You can even configure it to keep your clock a few minutes early, but with the assurance that you are exactly in advance a few minutes.
I have installed and am using for more than a month. It is very interesting to see all the clocks of the computer and cell phones exactly synchronized. It looks magic, and it avoids problems and the need to always be hitting each one!