Root (or jailbreak, or superuser permission) is required for the automatic synchronization. Without root only manual assisted synchronization is possible, please read "What can I do now?" section below to know how to keep your clock in sync with Rootless Mode.

Google doesn't allow user applications to change system time on any Android device. There was some hope that Android 2.2 will fix this issue, but it's unlikely to happen now as Google has published the following comment:

Hi, it is by design that applications can not change the time. There are many subtle aspects of security that can rely on the current time, such as certificate expiration, license management, etc. We do not want to allow third party applications to globally disrupt the system in this way.

At the moment setting system time is possible only on rooted devices. It's not a limitation of ClockSync, but a restriction of Android platform security. You will not find any other non-system application that can set time on Android without root.

What can I do now?

You can enable Rootless Mode by clicking on the button below. Once this mode is enabled ClockSync will notify you when the clock is off by the specified threshold (60 seconds is the default setting). When it happens, you'll see a notification, tapping on it will start the assisted synchronization process. The same process can be started by tapping on system time or from the ClockSync menu. Assisted sync opens system Date & Time settings and shows a hint at the bottom of the screen (what time/date should be set). You manually change the values to the suggested by ClockSync and assisted mode finishes automatically once the maximum possible precision is achieved. You can also cancel it by tapping on the notification in the status bar drop-down.

Rootless mode allows to set the clock with 1-30 seconds precision since most Android devices don't set/reset seconds when you change time, this method doesn't allow to fix offsets below 30 seconds. However, if your device resets seconds when you set time (most Samsung and some HTC devices), you can fix time with up to 1 second precision (enable "Device resets seconds" option). If you need higher precision or automatic synchronization, you will have to root your device. Basically, rootless mode is automatic offset check with specified interval and showing notification when the offset exceeds the threshold plus assisted manual synchronization. If you've rooted your device, disable Rootless mode in ClockSync settings to get automatic synchronization back.

Good news is that most Android devices can be rooted. Please note that rooting will usually void your warranty. Rooting method would depend on the particular device model and ROM. Please see How To Root Your Android Phone / Device for the detailed instructions. If you don't want or can't get root working on your device, then you will not be able to set system time with ClockSync, sorry.

You can also vote for the Android feature requests: Issue 4581: Allow user apps to set the system time and Issue 12497: Ability for applications to gain permission to set time. However, Google has already refused to fix it and chances are very low that it will be addressed in the future.

I have root, still doesn't work

Some devices have su binary which allows to perform commands with different user permissions from the adb shell or terminal. However, it will not necessarily run with the superuser permissions (UID=0) and it also doesn't allow Android applications to use root directly. Check that you have both su binary in /system/xbin or /system/bin and also Superuser.apk (Superuser Permissions application). I strongly recommend using Superuser 2.1 or later by ChainsDD. Please don't hesitate to contact me if you need help.

Market rating notes

Several users have put low ratings in Market because ClockSync was not able to change time on their devices without or with incorrectly working root. I hope for your understanding that it's not a problem of ClockSync and not because the developer was too dumb or lazy to find another way to set system clock. I've put a lot of time and efforts to make ClockSync the best one available in Android Market, free and without ads. I don't think that it deserves 1 star rating. I'm always ready to help with the possible problems for free, because I do care. Please mail me before setting low rating and uninstalling. ClockSync has been tested and is known to work correctly on many devices including Motorola Droid/Milestone, Google Nexus One, HTC Hero, HTC Magic, HTC Legend, HTC Desire, HTC EVO 4G, Samsung Galaxy S etc.