Use NSDateFormatter to format a date:
For example:
If you want date in this format:
... Tue, Dec 13, 2011 12:12 PM

you can use NSDateFormatter for this:
Here it goes:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"ccc, LLL d, YYYY HH:MM a"];
NSLog(@"%@", [dateFormatter stringFromDate:[NSDate date]]);

This will display the date in the format as shown in above example

Here are other parameters you can give to the NSDateFormatter to create your own formatted date:

a: AM/PM

A: 0~86399999 (Millisecond of Day)



c/cc: 1~7 (Day of Week)

ccc: Sun/Mon/Tue/Wed/Thu/Fri/Sat

cccc: Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday



d: 1~31 (0 padded Day of Month)

D: 1~366 (0 padded Day of Year)



e: 1~7 (0 padded Day of Week)

E~EEE: Sun/Mon/Tue/Wed/Thu/Fri/Sat

EEEE: Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday



F: 1~5 (0 padded Week of Month, first day of week = Monday)



g: Julian Day Number (number of days since 4713 BC January 1)

G~GGG: BC/AD (Era Designator Abbreviated)

GGGG: Before Christ/Anno Domini



h: 1~12 (0 padded Hour (12hr))

H: 0~23 (0 padded Hour (24hr))



k: 1~24 (0 padded Hour (24hr)

K: 0~11 (0 padded Hour (12hr))



L/LL: 1~12 (0 padded Month)

LLL: Jan/Feb/Mar/Apr/May/Jun/Jul/Aug/Sep/Oct/Nov/Dec

LLLL: January/February/March/April/May/June/July/August/September/October/November/December



m: 0~59 (0 padded Minute)

M/MM: 1~12 (0 padded Month)

MMM: Jan/Feb/Mar/Apr/May/Jun/Jul/Aug/Sep/Oct/Nov/Dec

MMMM: January/February/March/April/May/June/July/August/September/October/November/December



q/qq: 1~4 (0 padded Quarter)

qqq: Q1/Q2/Q3/Q4

qqqq: 1st quarter/2nd quarter/3rd quarter/4th quarter

Q/QQ: 1~4 (0 padded Quarter)

QQQ: Q1/Q2/Q3/Q4

QQQQ: 1st quarter/2nd quarter/3rd quarter/4th quarter



s: 0~59 (0 padded Second)

S: (rounded Sub-Second)



u: (0 padded Year)



v~vvv: (General GMT Timezone Abbreviation)

vvvv: (General GMT Timezone Name)



w: 1~53 (0 padded Week of Year, 1st day of week = Sunday, NB: 1st week of year starts from the last Sunday of last year)

W: 1~5 (0 padded Week of Month, 1st day of week = Sunday)



y/yyyy: (Full Year)

yy/yyy: (2 Digits Year)

Y/YYYY: (Full Year, starting from the Sunday of the 1st week of year)

YY/YYY: (2 Digits Year, starting from the Sunday of the 1st week of year)



z~zzz: (Specific GMT Timezone Abbreviation)

zzzz: (Specific GMT Timezone Name)

Z: +0000 (RFC 822 Timezone)