CODEWITHSUNDEEP
c#.netdatetime
Jeff Atwood
Jeff Atwood

Reputation: 63959

How do I calculate someone's age based on a DateTime type birthday?

Given a DateTime representing a person's birthday, how do I calculate their age in years?

Upvotes: 2266

Views: 850524

Answers (30)

DEEPU MATHEW
DEEPU MATHEW

Reputation: 14

this is the solution that I found works better, try this

DateTime dob,today;
    double age,month,days;
    dob=new DateTime(2023,12,05); 
    today= DateTime.Today;
    TimeSpan ts= today-dob;
    age=(int)(ts.Days/365.242374);
    if (dob.Month>=today.Month)
    {month=(12-dob.Month)+today.Month;}
    else{month=today.Month-dob.Month;}
    if(dob.Day>today.Day)
    {
     days=(31-dob.Day)+today.Day;
     month--;
    }
    else{ days=today.Day-dob.Day;}
    Console.WriteLine(age+" Years");
    Console.WriteLine(month+" Months");
    Console.WriteLine(days+" Days");

Upvotes: 0

Asif Ahmed Sourav
Asif Ahmed Sourav

Reputation: 19

static void Main()
{
    DateTime birthday = new DateTime(1990, 5, 15);
    int age = CalculateAge(birthday);
    Console.WriteLine($"The person is {age} years old.");
}

static int CalculateAge(DateTime birthday)
{
    DateTime today = DateTime.Today;
    int age = today.Year - birthday.Year;
    if (birthday > today.AddYears(-age))
    {
        age--;
    }
    return age;
}

Upvotes: 1

Md Shahriar
Md Shahriar

Reputation: 2786

var EndDate = new DateTime(2022, 4, 21);
var StartDate = new DateTime(1986, 4, 25);
Int32 Months = EndDate.Month - StartDate.Month;
Int32 Years = EndDate.Year - StartDate.Year;
Int32 Days = EndDate.Day - StartDate.Day;

if (Days < 0)
{
    --Months;
}

if (Months < 0)
{
    --Years;
    Months += 12;
}
            
string Ages = Years.ToString() + " Year(s) " + Months.ToString() + " Month(s) ";

Upvotes: 1

georgiosd
georgiosd

Reputation: 3059

Here's an answer making use of DateTimeOffset and manual math:

var diff = DateTimeOffset.Now - dateOfBirth;
var sinceEpoch = DateTimeOffset.UnixEpoch + diff;

return sinceEpoch.Year - 1970;

Upvotes: 1

Sam Saarian
Sam Saarian

Reputation: 1146

Why can't be simplified to check birth month and day?

First line (var year = end.Year - start.Year - 1;): assums that birthdate is not yet occurred on end year. Then check the month and day to see if it is occurred; add one more year.

No special treatment on leap year scenario. You cannot create a date (feb 29) as end date if it is not a leap year, so birthdate celebration will be counted if end date is on march 1th, not on deb 28th. The function below will cover this scenario as ordinary date.

    static int Get_Age(DateTime start, DateTime end)
    {
        var year = end.Year - start.Year - 1;
        if (end.Month < start.Month)
            return year;
        else if (end.Month == start.Month)
        {
            if (end.Day >= start.Day)
                return ++year;
            return year;
        }
        else
            return ++year;
    }

    static void Test_Get_Age()
    {
        var start = new DateTime(2008, 4, 10); // b-date, leap year BTY
        var end = new DateTime(2023, 2, 1); // end date is before the b-date
        var result1 = Get_Age(start, end);
        var success1 = result1 == 14; // true

        end = new DateTime(2023, 4, 10); // end date is on the b-date
        var result2 = Get_Age(start, end);
        var success2 = result2 == 15; // true

        end = new DateTime(2023, 6, 22); // end date is after the b-date
        var result3 = Get_Age(start, end);
        var success3 = result3 == 15; // true

        start = new DateTime(2008, 2, 29); // b-date is on feb 29
        end = new DateTime(2023, 2, 28); // end date is before the b-date
        var result4 = Get_Age(start, end);
        var success4 = result4 == 14; // true

        end = new DateTime(2020, 2, 29); // end date is on the b-date, on another leap year
        var result5 = Get_Age(start, end);
        var success5 = result5 == 12; // true
    }

Upvotes: 0

A.G.
A.G.

Reputation: 334

I would strongly recommend using a NuGet package called AgeCalculator since there are many things to consider when calculating age (leap years, time component etc) and only two lines of code does not cut it. The library gives you more than just a year. It even takes into consideration the time component at the calculation so you get an accurate age with years, months, days and time components. It is more advanced giving an option to consider Feb 29 in a leap year as Feb 28 in a non-leap year.

Upvotes: 3

Ruchir Gupta
Ruchir Gupta

Reputation: 1000

Don't know why nobody tried this:

        ushort age = (ushort)DateAndTime.DateDiff(DateInterval.Year, DateTime.Now.Date, birthdate);

All it requires is using Microsoft.VisualBasic; and reference to this assembly in the project (if not already referred).

Upvotes: 0

subcoder
subcoder

Reputation: 654

Simple and readable with complementary method

public static int getAge(DateTime birthDate)
{
    var today = DateTime.Today;
    var age = today.Year - birthDate.Year;
    var monthDiff = today.Month - birthDate.Month;
    var dayDiff = today.Day - birthDate.Day;

    if (dayDiff < 0)
    {
        monthDiff--;
    }
    if (monthDiff < 0)
    {
       age--;
    }
    return age;
}

Upvotes: 1

Wouter
Wouter

Reputation: 2958

A branchless solution:

public int GetAge(DateOnly birthDate, DateOnly today)
{
    return today.Year - birthDate.Year + (((today.Month << 5) + today.Day - ((birthDate.Month << 5) + birthDate.Day)) >> 31);
}

Upvotes: 0

user17413991
user17413991

Reputation:

This is a very simple approach:

int Age = DateTime.Today.Year - new DateTime(2000, 1, 1).Year;

Upvotes: 0

Rob
Rob

Reputation: 191

One could compute 'age' (i.e. the 'westerner' way) this way:

public static int AgeInYears(this System.DateTime source, System.DateTime target)
  => target.Year - source.Year is int age && age > 0 && source.AddYears(age) > target ? age - 1 : age < 0 && source.AddYears(age) < target ? age + 1 : age;

If the direction of time is 'negative', the age will be negative also.

One can add a fraction, which represents the amount of age accumulated from target to the next birthday:

public static double AgeInTotalYears(this System.DateTime source, System.DateTime target)
{
  var sign = (source <= target ? 1 : -1);

  var ageInYears = AgeInYears(source, target); // The method above.

  var last = source.AddYears(ageInYears);
  var next = source.AddYears(ageInYears + sign);

  var fractionalAge = (double)(target - last).Ticks / (double)(next - last).Ticks * sign;

  return ageInYears + fractionalAge;
}

The fraction is the ratio of passed time (from the last birthday) over total time (to the next birthday).

Both of the methods work the same way whether going forward or backward in time.

Upvotes: 0

Wylan Osorio
Wylan Osorio

Reputation: 1166

var startDate = new DateTime(2015, 04, 05);//your start date
var endDate = DateTime.Now;
var years = 0;
while(startDate < endDate) 
{
     startDate = startDate.AddYears(1);
     if(startDate < endDate) 
     {
         years++;
     }
}

Upvotes: 0

musefan
musefan

Reputation: 48435

This is simple and appears to be accurate for my needs. I am making an assumption for the purpose of leap years that regardless of when the person chooses to celebrate the birthday they are not technically a year older until 365 days have passed since their last birthday (i.e 28th February does not make them a year older).

DateTime now = DateTime.Today;
DateTime birthday = new DateTime(1991, 02, 03);//3rd feb

int age = now.Year - birthday.Year;

if (now.Month < birthday.Month || (now.Month == birthday.Month && now.Day < birthday.Day))//not had bday this year yet
  age--;

return age;

Upvotes: 10

user14273431
user14273431

Reputation:

I have no knowledge about DateTime but all I can do is this:

using System;
                    
public class Program
{
    public static int getAge(int month, int day, int year) {
        DateTime today = DateTime.Today;
        int currentDay = today.Day;
        int currentYear = today.Year;
        int currentMonth = today.Month;
        int age = 0;
        if (currentMonth < month) {
            age -= 1;
        } else if (currentMonth == month) {
            if (currentDay < day) {
                age -= 1;
            }
        }
        currentYear -= year;
        age += currentYear;
        return age;
    }
    public static void Main()
    {
        int ageInYears = getAge(8, 10, 2007);
        Console.WriteLine(ageInYears);
    }
}

A little confusing, but looking at the code more carefully, it will all make sense.

Upvotes: 0

S M Abrar Jahin
S M Abrar Jahin

Reputation: 14588

I think this problem can be solved with an easier way like this-

The class can be like-

using System;

namespace TSA
{
    class BirthDay
    {
        double ageDay;
        public BirthDay(int day, int month, int year)
        {
            DateTime birthDate = new DateTime(year, month, day);
            ageDay = (birthDate - DateTime.Now).TotalDays; //DateTime.UtcNow
        }

        internal int GetAgeYear()
        {
            return (int)Math.Truncate(ageDay / 365);
        }

        internal int GetAgeMonth()
        {
            return (int)Math.Truncate((ageDay % 365) / 30);
        }
    }
}

And calls can be like-

BirthDay b = new BirthDay(1,12,1990);
int year = b.GetAgeYear();
int month = b.GetAgeMonth();

Upvotes: -1

Alexander D&#237;az
Alexander D&#237;az

Reputation: 531

int Age = new DateTime((DateTime.Now - BirthDate).Ticks).Year -1;
Console.WriteLine("Age {0}", Age);

Upvotes: 0

CathalMF
CathalMF

Reputation: 10055

This is the easiest way to answer this in a single line.

DateTime Dob = DateTime.Parse("1985-04-24");
 
int Age = DateTime.MinValue.AddDays(DateTime.Now.Subtract(Dob).TotalHours/24 - 1).Year - 1;

This also works for leap years.

Upvotes: 5

Mike Polen
Mike Polen

Reputation: 3596

An easy to understand and simple solution.

// Save today's date.
var today = DateTime.Today;

// Calculate the age.
var age = today.Year - birthdate.Year;

// Go back to the year in which the person was born in case of a leap year
if (birthdate.Date > today.AddYears(-age)) age--;

However, this assumes you are looking for the western idea of the age and not using East Asian reckoning.

Upvotes: 2427

user1210708
user1210708

Reputation: 523

Here is a function that is serving me well. No calculations , very simple.

    public static string ToAge(this DateTime dob, DateTime? toDate = null)
    {
        if (!toDate.HasValue)
            toDate = DateTime.Now;
        var now = toDate.Value;

        if (now.CompareTo(dob) < 0)
            return "Future date";

        int years = now.Year - dob.Year;
        int months = now.Month - dob.Month;
        int days = now.Day - dob.Day;

        if (days < 0)
        {
            months--;
            days = DateTime.DaysInMonth(dob.Year, dob.Month) - dob.Day + now.Day;
        }

        if (months < 0)
        {
            years--;
            months = 12 + months;
        }


        return string.Format("{0} year(s), {1} month(s), {2} days(s)",
            years,
            months,
            days);
    }

And here is a unit test:

    [Test]
    public void ToAgeTests()
    {
        var date = new DateTime(2000, 1, 1);
        Assert.AreEqual("0 year(s), 0 month(s), 1 days(s)", new DateTime(1999, 12, 31).ToAge(date));
        Assert.AreEqual("0 year(s), 0 month(s), 0 days(s)", new DateTime(2000, 1, 1).ToAge(date));
        Assert.AreEqual("1 year(s), 0 month(s), 0 days(s)", new DateTime(1999, 1, 1).ToAge(date));
        Assert.AreEqual("0 year(s), 11 month(s), 0 days(s)", new DateTime(1999, 2, 1).ToAge(date));
        Assert.AreEqual("0 year(s), 10 month(s), 25 days(s)", new DateTime(1999, 2, 4).ToAge(date));
        Assert.AreEqual("0 year(s), 10 month(s), 1 days(s)", new DateTime(1999, 2, 28).ToAge(date));

        date = new DateTime(2000, 2, 15);
        Assert.AreEqual("0 year(s), 0 month(s), 28 days(s)", new DateTime(2000, 1, 18).ToAge(date));
    }

Upvotes: 3

Alexander
Alexander

Reputation: 46

Very simple answer

        DateTime dob = new DateTime(1991, 3, 4); 
        DateTime now = DateTime.Now; 
        int dobDay = dob.Day, dobMonth = dob.Month; 
        int add = -1; 
        if (dobMonth < now.Month)
        {
            add = 0;
        }
        else if (dobMonth == now.Month)
        {
            if(dobDay <= now.Day)
            {
                add = 0;
            }
            else
            {
                add = -1;
            }
        }
        else
        {
            add = -1;
        } 
        int age = now.Year - dob.Year + add;

Upvotes: 0

Nick Berardi
Nick Berardi

Reputation: 54894

The best way that I know of because of leap years and everything is:

DateTime birthDate = new DateTime(2000,3,1);
int age = (int)Math.Floor((DateTime.Now - birthDate).TotalDays / 365.25D);

Upvotes: 56

Michael Stum
Michael Stum

Reputation: 181044

Another function, not by me but found on the web and refined it a bit:

public static int GetAge(DateTime birthDate)
{
    DateTime n = DateTime.Now; // To avoid a race condition around midnight
    int age = n.Year - birthDate.Year;

    if (n.Month < birthDate.Month || (n.Month == birthDate.Month && n.Day < birthDate.Day))
        age--;

    return age;
}

Just two things that come into my mind: What about people from countries that do not use the Gregorian calendar? DateTime.Now is in the server-specific culture I think. I have absolutely zero knowledge about actually working with Asian calendars and I do not know if there is an easy way to convert dates between calendars, but just in case you're wondering about those Chinese guys from the year 4660 :-)

Upvotes: 95

James Curran
James Curran

Reputation: 103555

My suggestion

int age = (int) ((DateTime.Now - bday).TotalDays/365.242199);

That seems to have the year changing on the right date. (I spot tested up to age 107.)

Upvotes: 98

SillyMonkey
SillyMonkey

Reputation: 1334

Here's a one-liner:

int age = new DateTime(DateTime.Now.Subtract(birthday).Ticks).Year-1;

Upvotes: 52

RMA
RMA

Reputation: 231

Here is a test snippet:

DateTime bDay = new DateTime(2000, 2, 29);
DateTime now = new DateTime(2009, 2, 28);
MessageBox.Show(string.Format("Test {0} {1} {2}",
                CalculateAgeWrong1(bDay, now),      // outputs 9
                CalculateAgeWrong2(bDay, now),      // outputs 9
                CalculateAgeCorrect(bDay, now),     // outputs 8
                CalculateAgeCorrect2(bDay, now)));  // outputs 8

Here you have the methods:

public int CalculateAgeWrong1(DateTime birthDate, DateTime now)
{
    return new DateTime(now.Subtract(birthDate).Ticks).Year - 1;
}

public int CalculateAgeWrong2(DateTime birthDate, DateTime now)
{
    int age = now.Year - birthDate.Year;

    if (now < birthDate.AddYears(age))
        age--;

    return age;
}

public int CalculateAgeCorrect(DateTime birthDate, DateTime now)
{
    int age = now.Year - birthDate.Year;

    if (now.Month < birthDate.Month || (now.Month == birthDate.Month && now.Day < birthDate.Day))
        age--;

    return age;
}

public int CalculateAgeCorrect2(DateTime birthDate, DateTime now)
{
    int age = now.Year - birthDate.Year;

    // For leap years we need this
    if (birthDate > now.AddYears(-age)) 
        age--;
    // Don't use:
    // if (birthDate.AddYears(age) > now) 
    //     age--;

    return age;
}

Upvotes: 426

azamsharp
azamsharp

Reputation: 20096

This may work:

public override bool IsValid(DateTime value)
{
    _dateOfBirth =  value;
    var yearsOld = (double) (DateTime.Now.Subtract(_dateOfBirth).TotalDays/365);
    if (yearsOld > 18)
        return true;
    return false;
}

Upvotes: 4

Archit
Archit

Reputation: 650

How come the MSDN help did not tell you that? It looks so obvious:

System.DateTime birthTime = AskTheUser(myUser); // :-)
System.DateTime now = System.DateTime.Now;
System.TimeSpan age = now - birthTime; // As simple as that
double ageInDays = age.TotalDays; // Will you convert to whatever you want yourself?

Upvotes: 1

vulcan raven
vulcan raven

Reputation: 33592

With fewer conversions and UtcNow, this code can take care of someone born on the Feb 29 in a leap year:

public int GetAge(DateTime DateOfBirth)
{
    var Now = DateTime.UtcNow;
    return Now.Year - DateOfBirth.Year -
        (
            (
                Now.Month > DateOfBirth.Month ||
                (Now.Month == DateOfBirth.Month && Now.Day >= DateOfBirth.Day)
            ) ? 0 : 1
        );
}

Upvotes: 2

Pratik Bhoir
Pratik Bhoir

Reputation: 2144

A one-liner answer:

DateTime dateOfBirth = Convert.ToDateTime("01/16/1990");
var age = ((DateTime.Now - dateOfBirth).Days) / 365;

Upvotes: -3

mjb
mjb

Reputation: 7969

This is one of the most accurate answers that is able to resolve the birthday of 29th of Feb compared to any year of 28th Feb.

public int GetAge(DateTime birthDate)
{
    int age = DateTime.Now.Year - birthDate.Year;

    if (birthDate.DayOfYear > DateTime.Now.DayOfYear)
        age--;

    return age;
}

Upvotes: 16

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