C # Date formatting

Format Pattern Description
A day in the D month. One-digit date has no leading zeros.
DD a day of the month. A one-digit date has a leading zero.
The abbreviated name of the day of the DDD week, defined in Abbreviateddaynames.
dddd the full name of the day of the week, as defined in DayNames.
M-month number. One-digit month has no leading zeros.
MM month number. One-digit month has a leading zero.
Abbreviated name of the MMM month, defined in AbbreviatedMonthNames.
The full name of the MMMM month, as defined in MonthNames.
Y does not contain the year of the era. If the year that does not contain an era is less than 10, the year is displayed without leading zeros.
YY does not contain the year of the era. If the year that does not contain an era is less than 10, the year with leading zeros is displayed.
The YYYY includes the four-digit year of the era.
GG period or ERA. If the date to be formatted does not have an associated period or era string, the pattern is ignored.
H 12 Hour hour system. One-digit hours do not have leading zeros.
HH 12-hour hour. One-digit hours have leading zeros.
H 24 hour hour system. One-digit hours do not have leading zeros.
HH 24-hour hour. One-digit hours have leading zeros.
M minutes. A single-digit number of minutes does not have a leading zero.
MM minutes. A single-digit number of minutes has a leading zero.
s seconds. The number of seconds in a single digit does not have a leading zero.
SS seconds. The number of seconds of one digit has a leading zero.
The fractional precision of the F-second is one digit. The remaining digits are truncated.
The fractional precision of the FF seconds is two bits. The remaining digits are truncated.
The fractional precision of FFF seconds is three bits. The remaining digits are truncated.
The fractional precision of ffff seconds is four bits. The remaining digits are truncated.
The fractional precision of fffff seconds is five bits. The remaining digits are truncated.
The fractional precision of ffffff seconds is six bits. The remaining digits are truncated.
The fractional precision of fffffff seconds is seven bits. The remaining digits are truncated.
t the am/pm defined in AMDesignator or PMDesignator indicates the first character of the item, if one exists.
The AM/PM indicated by the TT in AMDesignator or PMDesignator (if present).
The Z Time zone offset ("+" or "-" followed by hours only). One-digit hours do not have leading zeros. For example, Pacific Standard Time is "-8".
ZZ Time zone offset ("+" or "-" followed by hours only). One-digit hours have leading zeros. For example, Pacific Standard Time is "-08".
The ZZZ Full time zone offset ("+" or "-" followed by hours and minutes). The number of hours and minutes of a single digit has a leading zero. For example, Pacific Standard Time is " -08:00".
: The default time delimiter defined in TimeSeparator.
/The default date delimiter defined in DateSeparator.
% c where C is the format pattern (if used alone). You can omit the "%" character if the format pattern is merged with literal characters or other format patterns.
c where c is any character. Displays the characters as they are originally defined. To display a backslash character, use "\".

Only the format patterns listed in the second table above can be used to create custom patterns, and the standard format characters listed in the first table cannot be used to create custom patterns. The custom pattern is at least two characters long;

DateTime.ToString ("D") returns a DateTime value; "D" is a standard short date pattern.
DateTime.ToString ("%d") returns the day of the month; "%d" is a custom pattern.
DateTime.ToString ("D") returns the day of the month followed by a blank character, and "D" is a custom pattern.

More convenient is that the above parameters can be arbitrarily combined, and will not be wrong, try more, will definitely find the time format you want
To get the time in this format for June 2005
It can be written like this:
Date. ToString ("yyyy mm month", Datetimeformatinfo.invariantinfo)

Reproduced from: http://www.cnblogs.com/emanlee/archive/2008/01/20/1046022.html ******************

C # Date formatting