docs(readme): clarify GUI nature, admin requirement, related link to time-mocker

README.md

@@ -1,15 +1,27 @@
 # time-changer
 
-Small Go tool to easily change the Windows system time from the command line.
+GUI tool written in Go (Fyne) to change the Windows system time from the desktop.
+
+> **Note:** Must be run as Administrator — Windows requires elevated privileges to set the system clock.
 
 ## Quick start
 
 ```bash
 go build -o time-changer.exe .
-# Run as Administrator:
+# Right-click → Run as Administrator:
-time-changer.exe "2025-01-15 08:30:00"
+time-changer.exe
 ```
 
+## Usage
+
+The app presents a calendar and time picker. Select the target date and time, then confirm to apply it as the new system time.
+
+Supported date selection: year/month/day via calendar widget; hours, minutes, seconds via dropdowns.
+
+## Related
+
+- [time-mocker](https://github.com/tiennm99/time-mocker) — injects fake time into a running process without changing the system clock (different approach to the same problem of time-dependent testing).
+
 ## License
 
 Apache-2.0 — see [LICENSE](LICENSE).