How can I visualize the way various DateTime formats will display?

Question

I want to be able to quickly reference how various DateTime formats will appear, rather than embark upon a laborious process of edit, compile, gawk, and recurse until satisf

Answer 1

Custom DateTime Formatting

There are following custom format specifiers y (year), M (month), d (day), h (hour 12), H (hour 24), m (minute), s (second), f (second fraction), F (second fraction, trailing zeroes are trimmed), t (P.M or A.M) and z (time zone).

Following examples demonstrate how are the format specifiers rewritten to the output. [C#]

    // create date time 2008-03-09 16:05:07.123
    DateTime dt = new DateTime(2008, 3, 9, 16, 5, 7, 123);
    String.Format("{0:y yy yyy yyyy}", dt);  // "8 08 008 2008"   year
    String.Format("{0:M MM MMM MMMM}", dt);  // "3 03 Mar March"  month
    String.Format("{0:d dd ffffd ffffdd}", dt);  // "9 09 Sun Sunday" day
    String.Format("{0:h hh H HH}",     dt);  // "4 04 16 16"      hour 12/24
    String.Format("{0:m mm}",          dt);  // "5 05"            minute
    String.Format("{0:s ss}",          dt);  // "7 07"            second
    String.Format("{0:f ff fff ffff}", dt);  // "1 12 123 1230"   sec.fraction
    String.Format("{0:F FF FFF FFFF}", dt);  // "1 12 123 123"    without zeroes
    String.Format("{0:t tt}",          dt);  // "P PM"            A.M. or P.M.
    String.Format("{0:z zz zzz}",      dt);  // "-6 -06 -06:00"   time zone

You can use also date separator / (slash) and time sepatator : (colon). These characters will be rewritten to characters defined in the current DateTimeForma­tInfo.DateSepa­rator and DateTimeForma­tInfo.TimeSepa­rator.

    // date separator in german culture is "." (so "/" changes to ".")
    String.Format("{0:d/M/yyyy HH:mm:ss}", dt); // "9/3/2008 16:05:07" - english (en-US)
    String.Format("{0:d/M/yyyy HH:mm:ss}", dt); // "9.3.2008 16:05:07" - german (de-DE)

Here are some examples of custom date and time formatting:

    // month/day numbers without/with leading zeroes
    String.Format("{0:M/d/yyyy}", dt);            // "3/9/2008"
    String.Format("{0:MM/dd/yyyy}", dt);          // "03/09/2008"

    // day/month names
    String.Format("{0:ffffd, MMM d, yyyy}", dt);    // "Sun, Mar 9, 2008"
    String.Format("{0:ffffdd, MMMM d, yyyy}", dt);  // "Sunday, March 9, 2008"

    // two/four digit year
    String.Format("{0:MM/dd/yy}", dt);            // "03/09/08"
    String.Format("{0:MM/dd/yyyy}", dt);          // "03/09/2008"

Standard DateTime Formatting

In DateTimeForma­tInfo there are defined standard patterns for the current culture. For example property ShortTimePattern is string that contains value h:mm tt for en-US culture and value HH:mm for de-DE culture.

Following examples show usage of standard format specifiers in String.Format method and the resulting output.

    String.Format("{0:t}", dt);  //"4:05 PM"                           ShortTime
    String.Format("{0:d}", dt);  //"3/9/2008"                          ShortDate
    String.Format("{0:T}", dt);  //"4:05:07 PM"                        LongTime
    String.Format("{0:D}", dt);  //"Sunday, March 09, 2008"            LongDate
    String.Format("{0:f}", dt);  //"Sunday, March 09, 2008 4:05 PM"    LongDate+ShortTime
    String.Format("{0:F}", dt);  //"Sunday, March 09, 2008 4:05:07 PM" FullDateTime
    String.Format("{0:g}", dt);  //"3/9/2008 4:05 PM"                  ShortDate+ShortTime
    String.Format("{0:G}", dt);  //"3/9/2008 4:05:07 PM"               ShortDate+LongTime
    String.Format("{0:m}", dt);  //"March 09"                          MonthDay
    String.Format("{0:y}", dt);  //"March, 2008"                       YearMonth
    String.Format("{0:r}", dt);  //"Sun, 09 Mar 2008 16:05:07 GMT"     RFC1123
    String.Format("{0:s}", dt);  //"2008-03-09T16:05:07"               SortableDateTime
    String.Format("{0:u}", dt);  // "2008-03-09 16:05:07Z"             UniversalSortableDateTime