SimpleDateFormat() - How to Set a Pattern to SimpleDateFormat

public SimpleDateFormat (String pattern) was added in API level 1
Constructs a new SimpleDateFormat using the specified non-localized pattern and the DateFormatSymbols andCalendar for the user's default locale. See "Be wary of the default locale".
Parameters: pattern - the pattern.

1. Declare a SimpleDateFormat variable

2. Add the below line in the onCreate method. This will create the format of a 4-digit year, number month and the number day of the month.

try { 
    mySimpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
} catch (NullPointerException e) {
    e.printStackTrace();
} catch (IllegalArgumentException e) {
    e.printStackTrace();
}

3. Compile and run!

4. Other symbols you could use for the format are:

Symbol	Meaning	Kind	Example
D	day in year	(Number)	189
E	day of week	(Text)	E/EE/EEE:Tue, EEEE:Tuesday, EEEEE:T
F	day of week in month	(Number)	2 (2nd Wed in July)
G	era designator	(Text)	AD
H	hour in day (0-23)	(Number)	0
K	hour in am/pm (0-11)	(Number)	0
L	stand-alone month	(Text)	L:1 LL:01 LLL:Jan LLLL:January LLLLL:J
M	month in year	(Text)	M:1 MM:01 MMM:Jan MMMM:January MMMMM:J
S	fractional seconds	(Number)	978
W	week in month	(Number)	2
Z	time zone (RFC 822)	(Time Zone)	Z/ZZ/ZZZ:-0800 ZZZZ:GMT-08:00 ZZZZZ:-08:00
a	am/pm marker	(Text)	PM
c	stand-alone day of week	(Text)	c/cc/ccc:Tue, cccc:Tuesday, ccccc:T
d	day in month	(Number)	10
h	hour in am/pm (1-12)	(Number)	12
k	hour in day (1-24)	(Number)	24
m	minute in hour	(Number)	30
s	second in minute	(Number)	55
w	week in year	(Number)	27
y	year	(Number)	yy:10 y/yyy/yyyy:2010
z	time zone	(Time Zone)	z/zz/zzz:PST zzzz:Pacific Standard Time
'	escape for text	(Delimiter)	'Date=':Date=
''	single quote	(Literal)	'o''clock':o'clock

Resources:
http://developer.android.com/reference/java/text/SimpleDateFormat.html#SimpleDateFormat(java.lang.String)