DateTime DateTime.Month DateTime.Parse string.Format

`DateTime` format

Format codes represent time, and dates, in different ways. Many format patterns can be encountered—many can be handled easily in C#.

We encounter strange codes in DateTime formats like "M" and "dddd." Here the case of the letters, and the number of them, are important.

First example

Let us examine a simple C# program. Here we combine many format codes. We use a formatting string with DateTime and ToString.

Note The letters in the format string specify the output. The final part (in the example) describes the format patterns.

using System;

// Use current time, with a format string.
DateTime time = DateTime.Now;
string format = "MMM ddd d HH:mm yyyy";
Console.WriteLine(time.ToString(format));
Feb Fri 17 07:11 2023MMM     Three-letter month.
ddd     Three-letter day of the week.
d       Day of the month.
HH      Two-digit hours on 24-hour scale.
mm      Two-digit minutes.
yyyy    Four-digit year.

Modified format

Here we modify the format string to get different output. We change some of the fields. We also use Parse on the resulting string.

Also We need to specify a format string when using DateTime.ParseExact and TryParseExact.

using System;

// Use DateTime format to convert to string.
DateTime time = new DateTime(2000, 2, 10);
string format = "M/dd/yyyy";
string result = time.ToString(format);
Console.WriteLine("RESULT: {0}", result);

// Parse string back to DateTime.
DateTime parsed = DateTime.Parse(result);
Console.WriteLine("PARSED: {0}", parsed);RESULT: 2/10/2000
PARSED: 2/10/2000 12:00:00 AM

`Single`-`char` format

We use a char with ToString or DateTime.ParseExact to specify a preset format. These are standard formats. They are useful in many programs.

using System;

DateTime now = DateTime.Now;
Console.WriteLine(now.ToString("d"));
Console.WriteLine(now.ToString("D"));
Console.WriteLine(now.ToString("f"));
Console.WriteLine(now.ToString("F"));
Console.WriteLine(now.ToString("g"));
Console.WriteLine(now.ToString("G"));
Console.WriteLine(now.ToString("m"));
Console.WriteLine(now.ToString("M"));
Console.WriteLine(now.ToString("o"));
Console.WriteLine(now.ToString("O"));
Console.WriteLine(now.ToString("s"));
Console.WriteLine(now.ToString("t"));
Console.WriteLine(now.ToString("T"));
Console.WriteLine(now.ToString("u"));
Console.WriteLine(now.ToString("U"));
Console.WriteLine(now.ToString("y"));
Console.WriteLine(now.ToString("Y"));d    2/27/2009
D    Friday, February 27, 2009
f    Friday, February 27, 2009 12:11 PM
F    Friday, February 27, 2009 12:12:22 PM
g    2/27/2009 12:12 PM
G    2/27/2009 12:12:22 PM
m    February 27
M    February 27
o    2009-02-27T12:12:22.1020000-08:00
O    2009-02-27T12:12:22.1020000-08:00
s    2009-02-27T12:12:22
t    12:12 PM
T    12:12:22 PM
u    2009-02-27 12:12:22Z
U    Friday, February 27, 2009 8:12:22 PM
y    February, 2009
Y    February, 2009

`Date` strings

Here we see the ToLongDateString, ToLongTimeString, ToShortDateString, and ToShortTimeString methods on DateTime. These methods use formats.

Note These methods are equivalent to calling ToString with the lowercase and uppercase D and T methods.

Note 2 We find that the default ToString() on DateTime is equivalent to the "G" formatting string.

using System;

DateTime now = DateTime.Now;
// Equivalent to D.
Console.WriteLine(now.ToLongDateString());
// Equivalent to T.
Console.WriteLine(now.ToLongTimeString());
// Equivalent to d.
Console.WriteLine(now.ToShortDateString());
// Equivalent to t.
Console.WriteLine(now.ToShortTimeString());
Console.WriteLine(now.ToString());ToLongDateString     Friday, February 27, 2009
ToLongTimeString     12:16:59 PM
ToShortDateString    2/27/2009
ToShortTimeString    12:16 PM
ToString             2/27/2009 12:16:59 PM

Minutes format

We use the lowercase code "mm" for minutes. Two lowercase "mm" has a leading zero if the number is only one digit long. For minutes, we must use 2 chars.

Info Just one "m" does not return minutes—it returns the month and day. The previous version of this page had an error here.

using System;

// Create DateTime with 9 minutes.
DateTime nineMinutes = new DateTime(2020, 4, 5, 3, 9, 0);
Console.WriteLine("mm: {0}", nineMinutes.ToString("mm"));
mm: 09

Seconds format

Seconds are formatted with "fFs." The uppercase F changes how trailing zeros are displayed. And the lowercase "s" changes how leading zeros are displayed.

Tip Use the lowercase "f" to indicate the seconds to one digit length. Use "ff" to indicate the seconds to two digits.

Note The uppercase F patterns do the same but work differently on trailing zeros.

Also The lowercase "s" displays seconds. With ss we always want two digits, such as 00-59.

using System;
using static System.Console;

DateTime now = DateTime.Now;
// Use space after s to avoid one-char date format.
string result = now.ToString("s ");
WriteLine($"{now} [s] = {result}");
12/5/2015 2:04:17 PM [s] = 17

Hours format

For hours we use "j" and "H." You can use one or two characters. The lowercase "h" is used for a 12-hour clock. The uppercase H is a 24-hour clock.

using System;

// Create DateTime with 13 hours, or 1 PM.
var earlyAfternoon = new DateTime(2020, 1, 1, 13, 0, 0);
Console.WriteLine("HH: {0}", earlyAfternoon.ToString("HH"));
HH: 13

Day format

For days we use one to four "d" chars. One "d" and "dd" indicate the day of the month, while "ddd" and "dddd" indicate the day of the week, in a word.

using System;

DateTime time = new DateTime(2000, 1, 1);
// Console.WriteLine and string.Format can handle dates.
Console.WriteLine("Two letters: {0:ddd}", time);
Console.WriteLine("Three letters: {0:dddd}", time);Two letters: Sat
Three letters: Saturday

Complete day

Often we need to display the complete day of the week, and the four ds together will do this. With Console.WriteLine, we print all seven day strings we get from the dddd.

using System;

DateTime now = DateTime.Today;
for (int i = 0; i < 7; i++)
{
    Console.WriteLine(now.ToString("dddd"));
    now = now.AddDays(1);
}Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday

Three-letter days

We can display the day of the week in a three-letter form. Here we see a simple program that does this—results vary based on the current language.

using System;

DateTime now = DateTime.Today;
for (int i = 0; i < 7; i++)
{
    Console.WriteLine(now.ToString("ddd"));
    now = now.AddDays(1);
}Thu
Fri
Sat
Sun
Mon
Tue
Wed

Month format

The month is formatted with an uppercase M. One and two Ms display numeric representations. Three and four Ms display string representations.

using System;

// Get month for January.
DateTime test = new DateTime(2020, 1, 1);
Console.WriteLine("M:    {0}", test.ToString("M"));
Console.WriteLine("MM:   {0}", test.ToString("MM"));
Console.WriteLine("MMM:  {0}", test.ToString("MMM"));
Console.WriteLine("MMMM: {0}", test.ToString("MMMM"));M:    January 1
MM:   01
MMM:  Jan
MMMM: January

Era

We can display the date with the era or period—usually AD or BC. It is unlikely that you will need to use BC, except in a rare theoretical application. Here is what two gs will print.

using System;

// We are in A.D. era.
Console.WriteLine(DateTime.Now.ToString("gg"));
A.D.

AM, PM

When you specify one "t" you can get the first letter of the AM or PM string. This is equivalent to using Substring or getting the first char of the "tt" string.

Tip There is a space at the end of the format string—the value "t" can mean something else in the format string.

Next We show a program that gets the string AM or PM in DateTime ToString code.

Note There are no periods in the output of tt. If you require periods in your AM or PM, you would have to manipulate the string.

using System;

DateTime now = DateTime.Now;
for (int i = 0; i < 2; i++)
{
    Console.WriteLine(now.ToString("tt "));
    now = now.AddHours(12);
}PM
AM

Year

We can vary the number of digits displayed in the year string. We will want to use "y," yy, or yyyy for our programs. But five ys is also possible.

Tip Two ys is useful for a user-oriented program, but for back-end code, we will want to use four ys.

Info In almost all programs, we will not need three or five digits for the year, but these codes exist.

using System;

DateTime now = DateTime.Now;
Console.WriteLine(now.ToString("y "));
Console.WriteLine(now.ToString("yy"));
Console.WriteLine(now.ToString("yyy"));
Console.WriteLine(now.ToString("yyyy"));
Console.WriteLine(now.ToString("yyyyy"));23
23
2023
2023
02023

`FormatException`

We must pass a valid formatting string to ToString on a DateTime. If we pass something invalid, like an asterisk, we will get a FormatException.

using System;

const string invalid = "*";
string result = DateTime.Today.ToString(invalid);Unhandled Exception: System.FormatException: Input string was not in a correct format.
   at System.DateTimeFormat.GetRealFormat....

Null

When we format a DateTime with a format string that is null, empty, or missing, we get a default format. We can just omit the argument if we do not have a special format we need.

using System;

var date = new DateTime(2000, 1, 1);
Console.WriteLine("NULL FORMAT STRING:    {0}", date.ToString((string)null));
Console.WriteLine("EMPTY FORMAT STRING:   {0}", date.ToString(""));
Console.WriteLine("MISSING FORMAT STRING: {0}", date.ToString());NULL FORMAT STRING:    1/1/2000 12:00:00 AM
EMPTY FORMAT STRING:   1/1/2000 12:00:00 AM
MISSING FORMAT STRING: 1/1/2000 12:00:00 AM

`Parse`

To go from string to DateTime, we can use the Parse() and TryParse() methods. Format strings can be provided with ParseExact.

Many DateTime formats can be used. We covered single-letter preset format strings. And we handled more complicated, custom strings with character codes.

DateTime format