You can use SimpleDateFormat. Look these examples:
String sDate1="31/12/1998";
String sDate2 = "31-Dec-1998";
String sDate3 = "12 31, 1998";
String sDate4 = "Thu, Dec 31 1998";
String sDate5 = "Thu, Dec 31 1998 23:37:50";
String sDate6 = "31-Dec-1998 23:37:50";
SimpleDateFormat formatter1=new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat formatter2=new SimpleDateFormat("dd-MMM-yyyy");
SimpleDateFormat formatter3=new SimpleDateFormat("MM dd, yyyy");
SimpleDateFormat formatter4=new SimpleDateFormat("E, MMM dd yyyy");
SimpleDateFormat formatter5=new SimpleDateFormat("E, MMM dd yyyy HH:mm:ss");
SimpleDateFormat formatter6=new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss");
Date date1=formatter1.parse(sDate1);
Date date2=formatter2.parse(sDate2);
Date date3=formatter3.parse(sDate3);
Date date4=formatter4.parse(sDate4);
Date date5=formatter5.parse(sDate5);
Date date6=formatter6.parse(sDate6);
For this you will need import:
import java.text.SimpleDateFormat;
import java.util.Date;