The Comprehensive Guide to Custom DateTime String Formats in C#

When working with C#, we can convert a DateTime object to a string. If we don't specify any formatting options, the default DateTime string format will be outputted. However, C# gives us the power to completely customise how the DateTime object should be outputted using custom format specifiers.

How do I format DateTime objects?

There are a few ways that you can format a DateTime object when converting it to a string. We'll first go through some of these methods before going through how to use custom format strings to format DateTime objects.

DateTime.ToString()

This is probably the most common way of formatting a DateTime as a string in C#. It allows you to optionally pass the format to use as a string parameter. For example (click Run to run the example):

You can read more information here.

string.Format()

You are also able to specify how a string should be formatted using string.Format() by passing in the DateTime object as one of the objects to be inserted. For example (click Run to run the example):

You can read more here.

String Interpolation ($)

This is by far the neatest way to format a DateTime string in my opinion. It looks neat and is compact. Here's an example (click Run to run the example):

You can read more about string interpolation here.

Custom DateTime Format Strings

We are able to format a DateTime using a custom format string. A format string is simply a string in C# where sequences of characters (called format specifiers) in the string dictate what portions of the DateTime should be outputted and how they should be formatted. These format specifiers can be combined to output multiple portions of a DateTime object (as well as other objects in .NET) in a single string. This gives you granular control over how DateTime objects should be outputted.

Below is a table of all the different string sequences that can be used in custom format strings for DateTime objects (taken from here). There is a REPL below that you can use to test these format specifiers.

Here is a REPL that demonstrating all the above Format Specifiers. Feel free to experiment!

I hope you found this article informative. Please let me know if you have any suggestions, queries or criticisms.

Sources

• https://docs.microsoft.com/en-us/dotnet/standard/base-types/custom-date-and-time-format-strings