# Using the timesync library in Android applications
This tutorial illustrates how the timesync library can be used to synchronize time between a node.js server and an android application.
## Step 1:
Place the following index.html on your webserver which uses the timesync library and will be called from Java:
```HTML
```
## Step 2:
Add an invisible webview to your Android applications layout.xml:
```XML
```
## Step 3:
In your Acitivity's `onCreate` method retieve this webview and initialize time synchronization:
```Java
mWebView = (WebView) findViewById(R.id.webview);
WebSettings settings = mWebView.getSettings();
settings.setJavaScriptEnabled(true);
settings.setAllowFileAccessFromFileURLs(true);
settings.setAllowUniversalAccessFromFileURLs(true);
mWebView.loadUrl("http://" + serverIPPort);
mWebView.addJavascriptInterface(new CustomJavaScriptInterface(mWebView.getContext()), "Android");
```
## Step 4:
Define the `CustomJavaScriptInterface`:
```Java
public class CustomJavaScriptInterface {
Context mContext;
/**
* Instantiate the interface and set the context
*/
CustomJavaScriptInterface(Context c) {
mContext = c;
}
/**
* retrieve the server time
*/
@JavascriptInterface
public void getServerTime(final long time) {
Log.d(TAG, "Time is " + time);
MainActivity.serverTime = time;
}
@JavascriptInterface
public void getTimeOffset(final long offset) {
Log.d(TAG, "Time offset is " + offset);
MainActivity.timeOffset = offset;
}
}
```
## Step 5:
Add the following Java methods to your Activity to retrieve the server time and the time offset through your JavascriptInterface. As you can see, these methods use the `ts` variable of the HTML file on the server to set the server time within the Android Activity:
```Java
private long getServerTime() {
mWebView.loadUrl("javascript:Android.getServerTime(ts.now());");
return serverTime;
}
private long getTimeOffset() {
mWebView.loadUrl("javascript:Android.getTimeOffset(lastOffset);");
return timeOffset;
}
```
## Step 6:
Call the Java methods `getServerTime()` and `getTimeOffset` anywhere in your code to receive the synchronized time or the time offset.