Format Dates and Time using Apex in Salesforce

This post explains how to format dates and times using apex.
The below table contains the formatting codes.

Letter	Date or Time Piece	Examples
G	Era	G = AD
y	Year	yy = 09, yyyy = 2009
M	Month	MM = 08, MMM = Aug, MMMMM = August
w	Week in year	w = 35
W	Week in month	W = 3
D	Day in year	D = 235
d	Day in month	dd = 27
F	Day of week in month	F = 2
E	Day in week	E = Thu, EEEEE = Thursday
a	AM/PM	a = AM or PM
H	Hour in day (0-23)	HH = 23
k	Hour in day (1-24)	kk = 24
K	Hour in am/pm (0-11)	KK=11
h	Hour in am/pm (1-12)	hh = 12
m	Minutes in hour	mm = 30
s	Second in minute	ss = 55
S	Millisecond in second	SSS = 888
z	Time zone	z = EDT, zzzzz = Eastern Daylight Time
Z	Time zone offset	Z = -0400

Examples

DateTime dt = Datetime.now();
String strTimeInAMorPM = dt.format('MMMMM dd, yyyy hh:mm:ss a');
System.debug('time in am and pm ==> '+strTimeInAMorPM); 

String strTimeInWeek = dt.format('MMMMM dd, yyyy EEEE');
System.debug('strTimeInWeek ==> '+strTimeInWeek); 

String strTimezone = dt.format('MMMMM dd, yyyy z');
System.debug('strTimezone ==> '+strTimezone); 

Output