format in datetime

using System;
using System.Globalization;

public class MainClass {
   public static void Main(string[] args)  {
       DateTime dt = DateTime.Now;
       String[] format = {
           "d", "D",
           "f", "F",
           "g", "G",
           "m",
           "r",
           "s",
           "t", "T",
           "u", "U",
           "y",
           "dddd, MMMM dd yyyy",
           "ddd, MMM d /"'/"yy",
           "dddd, MMMM dd",
           "M/yy",
           "dd-MM-yy",
       };
       String date;
       for (int i = 0; i < format.Length; i++) {
           date = dt.ToString(format[i], DateTimeFormatInfo.InvariantInfo);
           Console.WriteLine(String.Concat(format[i], " :" , date));
       }
 
  /** Output.
   *
   * d :08/17/2000
   * D :Thursday, August 17, 2000
   * f :Thursday, August 17, 2000 16:32
   * F :Thursday, August 17, 2000 16:32:32
   * g :08/17/2000 16:32
   * G :08/17/2000 16:32:32
   * m :August 17
   * r :Thu, 17 Aug 2000 23:32:32 GMT
   * s :2000-08-17T16:32:32
   * t :16:32
   * T :16:32:32
   * u :2000-08-17 23:32:32Z
   * U :Thursday, August 17, 2000 23:32:32
   * y :August, 2000
   * dddd, MMMM dd yyyy :Thursday, August 17 2000
   * ddd, MMM d "'"yy :Thu, Aug 17 '00
   * dddd, MMMM dd :Thursday, August 17
   * M/yy :8/00
   * dd-MM-yy :17-08-00
   */
   }
}

Format Character	Associated Property/ Description
d	ShortDatePattern
D	LongDatePattern
f	Full date and time (long date and short time)
F	FullDateTimePattern (long date and long time)
g	General (short date and short time)
G	General (short date and long time)
m, M	MonthDayPattern
r, R	RFC1123Pattern
s	SortableDateTimePattern (based on ISO 8601) using local time
t	ShortTimePattern
T	LongTimePattern
u	UniversalSortableDateTimePattern using the format for universal time display
U	Full date and time (long date and long time) using universal time
y, Y	YearMonthPattern

The following table lists the patterns that can be combined to construct custom patterns. The patterns are case-sensitive; for example, "MM" is recognized, but "mm" is not. If the custom pattern contains white-space characters or characters enclosed in single quotation marks, the output string will also contain those characters. Characters not defined as part of a format pattern or as format characters are reproduced literally.

Format Pattern	Description
d	The day of the month. Single-digit days will not have a leading zero.
dd	The day of the month. Single-digit days will have a leading zero.
ddd	The abbreviated name of the day of the week, as defined in AbbreviatedDayNames.
dddd	The full name of the day of the week, as defined in DayNames.
M	The numeric month. Single-digit months will not have a leading zero.
MM	The numeric month. Single-digit months will have a leading zero.
MMM	The abbreviated name of the month, as defined in AbbreviatedMonthNames.
MMMM	The full name of the month, as defined in MonthNames.
y	The year without the century. If the year without the century is less than 10, the year is displayed with no leading zero.
yy	The year without the century. If the year without the century is less than 10, the year is displayed with a leading zero.
yyyy	The year in four digits, including the century.
gg	The period or era. This pattern is ignored if the date to be formatted does not have an associated period or era string.
h	The hour in a 12-hour clock. Single-digit hours will not have a leading zero.
hh	The hour in a 12-hour clock. Single-digit hours will have a leading zero.
H	The hour in a 24-hour clock. Single-digit hours will not have a leading zero.
HH	The hour in a 24-hour clock. Single-digit hours will have a leading zero.
m	The minute. Single-digit minutes will not have a leading zero.
mm	The minute. Single-digit minutes will have a leading zero.
s	The second. Single-digit seconds will not have a leading zero.
ss	The second. Single-digit seconds will have a leading zero.
f	The fraction of a second in single-digit precision. The remaining digits are truncated.
ff	The fraction of a second in double-digit precision. The remaining digits are truncated.
fff	The fraction of a second in three-digit precision. The remaining digits are truncated.
ffff	The fraction of a second in four-digit precision. The remaining digits are truncated.
fffff	The fraction of a second in five-digit precision. The remaining digits are truncated.
ffffff	The fraction of a second in six-digit precision. The remaining digits are truncated.
fffffff	The fraction of a second in seven-digit precision. The remaining digits are truncated.
t	The first character in the AM/PM designator defined in AMDesignator or PMDesignator, if any.
tt	The AM/PM designator defined in AMDesignator or PMDesignator, if any.
z	The time zone offset ("+" or "-" followed by the hour only). Single-digit hours will not have a leading zero. For example, Pacific Standard Time is "-8".
zz	The time zone offset ("+" or "-" followed by the hour only). Single-digit hours will have a leading zero. For example, Pacific Standard Time is "-08".
zzz	The full time zone offset ("+" or "-" followed by the hour and minutes). Single-digit hours and minutes will have leading zeros. For example, Pacific Standard Time is "-08:00".
:	The default time separator defined in TimeSeparator.
/	The default date separator defined in DateSeparator.
% c	Where c is a format pattern if used alone. The "%" character can be omitted if the format pattern is combined with literal characters or other format patterns.
/ c	Where c is any character. Displays the character literally. To display the backslash character, use "//".