How to Use DateOnly and TimeOnly in C#

In C#, DateOnly represents a date without time, and TimeOnly represents a time without date. You can create instances using constructors or parsing strings, and use their methods to manipulate or display date or time values separately.

Syntax

DateOnly stores only the date part (year, month, day). TimeOnly stores only the time part (hour, minute, second, millisecond).

You can create them using constructors or parse strings.

csharp

var date = new DateOnly(2024, 6, 15);
var time = new TimeOnly(14, 30, 0);

var parsedDate = DateOnly.Parse("2024-06-15");
var parsedTime = TimeOnly.Parse("14:30:00");

Example

This example shows how to create, display, and add days or hours using DateOnly and TimeOnly.

csharp

using System;

class Program
{
    static void Main()
    {
        DateOnly date = new DateOnly(2024, 6, 15);
        TimeOnly time = new TimeOnly(14, 30, 0);

        Console.WriteLine($"Date: {date}");
        Console.WriteLine($"Time: {time}");

        DateOnly nextDay = date.AddDays(1);
        TimeOnly nextHour = time.AddHours(1);

        Console.WriteLine($"Next day: {nextDay}");
        Console.WriteLine($"Next hour: {nextHour}");
    }
}

Output

Date: 2024-06-15
Time: 14:30:00
Next day: 2024-06-16
Next hour: 15:30:00

Common Pitfalls

• Trying to use DateOnly or TimeOnly where DateTime is expected can cause errors because they are different types.
• They do not store timezone or offset information.
• Parsing strings must match expected formats or use culture settings.

csharp

/* Wrong: assigning DateOnly to DateTime */
// DateTime dt = new DateOnly(2024, 6, 15); // Error

/* Right: convert DateOnly to DateTime */
DateOnly d = new DateOnly(2024, 6, 15);
DateTime dt = d.ToDateTime(TimeOnly.MinValue);

Quick Reference

Feature	DateOnly	TimeOnly
Represents	Date only (year, month, day)	Time only (hour, minute, second, ms)
Create with	new DateOnly(year, month, day)	new TimeOnly(hour, minute, second)
Parse from string	DateOnly.Parse("yyyy-MM-dd")	TimeOnly.Parse("HH:mm:ss")
Add time	AddDays(int days)	AddHours(int hours)
Convert to DateTime	ToDateTime(TimeOnly time)	ToDateTime(DateOnly date)

Key Takeaways

Use DateOnly to work with dates without times and TimeOnly for times without dates.

Create instances using constructors or parse from strings matching the expected format.

DateOnly and TimeOnly do not include timezone info; use DateTime for full date-time with timezone.

Convert DateOnly or TimeOnly to DateTime when needed using ToDateTime method.

Be careful not to mix DateOnly/TimeOnly directly with DateTime without conversion.