Using date time fields in android(Java) against a C# api

ApiManager.java

package com.myapphelper.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Date;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.conn.params.ConnManagerParams;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.HttpConnectionParams;
import org.apache.http.params.HttpParams;
import org.apache.http.util.EntityUtils;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.myapp.Constants;
import com.myapp.RecordModel;
import com.myapp.AppHelper;

public class ApiManager {
  static final int HTTP_REQUEST_TIMEOUT_MS = 30 * 1000;
  
	private final Gson gson = new GsonBuilder().registerTypeAdapter(Date.class, new UtcDateGsonAdapter()).create();
	
	private final HttpClient httpClient = new DefaultHttpClient();
  private final HttpParams httpParams = httpClient.getParams();
  
  public ApiManager() {
      HttpConnectionParams.setConnectionTimeout(httpParams, HTTP_REQUEST_TIMEOUT_MS);
      HttpConnectionParams.setSoTimeout(httpParams, HTTP_REQUEST_TIMEOUT_MS);
      ConnManagerParams.setTimeout(httpParams, HTTP_REQUEST_TIMEOUT_MS);
  }
  public Gson getGson() { return gson; }
  public HttpResponse execute(HttpUriRequest request) throws ClientProtocolException, IOException {
	  request.setHeader("Accept", "application/json");
    request.setHeader("Content-Type", "application/json");
    return httpClient.execute(request);
	}
	
  public List<RecordModel> getRecords(String recid, Date starting, Date ending) throws ClientProtocolException, IOException {
    HttpGet get = new HttpGet("http://www.mywebste.com/api/records?recid="
      + recid + "&start=" + AppHelper.unixToWindowsTime(starting.getTime())
      + "&end=" + AppHelper.unixToWindowsTime(ending.getTime()));
    HttpResponse response = execute(get);
    if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
      String responseString = EntityUtils.toString(response.getEntity());
      List<RecordModel> records = getGson().fromJson(responseString, Constants.RecordListType);
      return records;
    }
    return null;
  }
}

AppHelper.java

package com.myapphelper.util;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;

public class AppHelper {
	
	public static final long UNIX_WINDOWS_TIME_DIFF_MILLIS = 62135596800000L;
	public static final int TICKS_PER_MILLISECOND = 10000;
	
	public static long unixToWindowsTime(long unixMillis) {
		return ((unixMillis + UNIX_WINDOWS_TIME_DIFF_MILLIS) * TICKS_PER_MILLISECOND);
	}
	
	public static long windowsToUnixTime(long windowsTicks) {
		return ((windowsTicks / TICKS_PER_MILLISECOND) -  UNIX_WINDOWS_TIME_DIFF_MILLIS);
	}
	
	public static Date toUtcTime(long localTimeMillis) {
		Calendar c = Calendar.getInstance();
		int offset = c.getTimeZone().getOffset(c.getTimeInMillis());
		GregorianCalendar utc = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
		
		utc.setTimeInMillis(localTimeMillis);
		utc.add(Calendar.MILLISECOND, -offset);
		return utc.getTime();
	}

}

UtcDateGsonAdapter.java

package com.myapphelper.util;

import java.lang.reflect.Type;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

public class UtcDateGsonAdapter implements JsonDeserializer<Date>, JsonSerializer<Date> {
	private final DateFormat dateFormat;

	public UtcDateGsonAdapter() {
		dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US);
		dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
	}

	@Override
	public synchronized Date deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext jsonDeserializationContext) {
		try {
			String str = jsonElement.getAsString();
			if (str.contains(".")) {
				str = str.substring(0, str.indexOf("."));
				str += "Z";
			}
			
			return dateFormat.parse(str);
		} catch (java.text.ParseException e) {
			e.printStackTrace();
			return null;
		}
	}

	@Override
	public JsonElement serialize(Date date, Type type, JsonSerializationContext jsonSerializationContext) {
		return new JsonPrimitive(dateFormat.format(date));
	}
}