By default, SyncTime appears both in the Dock and to the right of the menu bar. Only apps that appear in the Dock are listed in the Force Quit window ( > Force Quit). If you disabled the option to show SyncTime in the Dock, in order to force quit it, follow these steps:

1. Open the Activity Monitor app (from /Applications/Utilities).
2. Type the name of the app in the search field.
3. Click the Terminate button with a cross icon in the toolbar and confirm the alert dialog that appears afterwards.