Android get date before 7 days (one week)

Question

HI

How to get date before one week from now in android in this format:

       SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

ex: now 2010-09-19 HH:mm:ss, before one week 2010-09-12 HH:mm:ss

Thanks

Answer 1

Parse the date:

Date myDate = dateFormat.parse(dateString);

And then either figure out how many milliseconds you need to subtract:

Date newDate = new Date(myDate.getTime() - 604800000L); // 7 * 24 * 60 * 60 * 1000

Or use the API provided by the java.util.Calendar class:

Calendar calendar = Calendar.getInstance();
calendar.setTime(myDate);
calendar.add(Calendar.DAY_OF_YEAR, -7);
Date newDate = calendar.getTime();

Then, if you need to, convert it back to a String:

String date = dateFormat.format(newDate);

Answer 2

I can see two ways:

1. Use a GregorianCalendar:

   Calendar someDate = GregorianCalendar.getInstance();
   someDate.add(Calendar.DAY_OF_YEAR, -7);
   SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   String formattedDate = dateFormat.format(someDate);
   

2. Use a android.text.format.Time:

   long yourDateMillis = System.currentTimeMillis() - (7 * 24 * 60 * 60 * 1000);
   Time yourDate = new Time();
   yourDate.set(yourDateMillis);
   String formattedDate = yourDate.format("%Y-%m-%d %H:%M:%S");
   

Solution 1 is the "official" java way, but using a GregorianCalendar can have serious performance issues so Android engineers have added the android.text.format.Time object to fix this.