[C#] 誰かの年齢をC#でどのように計算するのですか?


Answers

これは奇妙な方法ですが、日付をyyyymmddフォーマットし、現在の日付から生年月日を引いた場合、年齢を指定した最後の4桁を削除してください:)

私はC#を知らないが、これはどの言語でも動作すると信じている。

20080814 - 19800703 = 280111 

最後の4桁= 28ます。

C#コード:

int now = int.Parse(DateTime.Now.ToString("yyyyMMdd"));
int dob = int.Parse(dateOfBirth.ToString("yyyyMMdd"));
int age = (now - dob) / 10000;

あるいは、すべての型変換を拡張メソッドの形式で行う必要はありません。 エラーチェック省略:

public static Int32 GetAge(this DateTime dateOfBirth)
{
    var today = DateTime.Today;

    var a = (today.Year * 100 + today.Month) * 100 + today.Day;
    var b = (dateOfBirth.Year * 100 + dateOfBirth.Month) * 100 + dateOfBirth.Day;

    return (a - b) / 10000;
}
Question

人の誕生日を表すDateTime与えられると、年数はどのように計算されますか?




それを単純なままにする(そして、おそらくばかげて:))。

DateTime birth = new DateTime(1975, 09, 27, 01, 00, 00, 00);
TimeSpan ts = DateTime.Now - birth;
Console.WriteLine("You are approximately " + ts.TotalSeconds.ToString() + " seconds old.");



私はこれに取り組むために少し時間を費やして、年、月、日で誰かの年齢を計算するためにこれを思いついた。 私は2月29日の問題に対して試練を重ね、閏年を迎えました。それはうまくいくようです。私はフィードバックを感謝します:

public void LoopAge(DateTime myDOB, DateTime FutureDate)
{
    int years = 0;
    int months = 0;
    int days = 0;

    DateTime tmpMyDOB = new DateTime(myDOB.Year, myDOB.Month, 1);

    DateTime tmpFutureDate = new DateTime(FutureDate.Year, FutureDate.Month, 1);

    while (tmpMyDOB.AddYears(years).AddMonths(months) < tmpFutureDate)
    {
        months++;

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

    if (FutureDate.Day >= myDOB.Day)
    {
        days = days + FutureDate.Day - myDOB.Day;
    }
    else
    {
        months--;

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

        days +=
            DateTime.DaysInMonth(
                FutureDate.AddMonths(-1).Year, FutureDate.AddMonths(-1).Month
            ) + FutureDate.Day - myDOB.Day;

    }

    //add an extra day if the dob is a leap day
    if (DateTime.IsLeapYear(myDOB.Year) && myDOB.Month == 2 && myDOB.Day == 29)
    {
        //but only if the future date is less than 1st March
        if (FutureDate >= new DateTime(FutureDate.Year, 3, 1))
            days++;
    }

}



I used ScArcher2's solution for an accurate Year calculation of a persons age but I needed to take it further and calculate their Months and Days along with the Years.

    public static Dictionary<string,int> CurrentAgeInYearsMonthsDays(DateTime? ndtBirthDate, DateTime? ndtReferralDate)
    {
        //----------------------------------------------------------------------
        // Can't determine age if we don't have a dates.
        //----------------------------------------------------------------------
        if (ndtBirthDate == null) return null;
        if (ndtReferralDate == null) return null;

        DateTime dtBirthDate = Convert.ToDateTime(ndtBirthDate);
        DateTime dtReferralDate = Convert.ToDateTime(ndtReferralDate);

        //----------------------------------------------------------------------
        // Create our Variables
        //----------------------------------------------------------------------
        Dictionary<string, int> dYMD = new Dictionary<string,int>();
        int iNowDate, iBirthDate, iYears, iMonths, iDays;
        string sDif = "";

        //----------------------------------------------------------------------
        // Store off current date/time and DOB into local variables
        //---------------------------------------------------------------------- 
        iNowDate = int.Parse(dtReferralDate.ToString("yyyyMMdd"));
        iBirthDate = int.Parse(dtBirthDate.ToString("yyyyMMdd"));

        //----------------------------------------------------------------------
        // Calculate Years
        //----------------------------------------------------------------------
        sDif = (iNowDate - iBirthDate).ToString();
        iYears = int.Parse(sDif.Substring(0, sDif.Length - 4));

        //----------------------------------------------------------------------
        // Store Years in Return Value
        //----------------------------------------------------------------------
        dYMD.Add("Years", iYears);

        //----------------------------------------------------------------------
        // Calculate Months
        //----------------------------------------------------------------------
        if (dtBirthDate.Month > dtReferralDate.Month)
            iMonths = 12 - dtBirthDate.Month + dtReferralDate.Month - 1;
        else
            iMonths = dtBirthDate.Month - dtReferralDate.Month;

        //----------------------------------------------------------------------
        // Store Months in Return Value
        //----------------------------------------------------------------------
        dYMD.Add("Months", iMonths);

        //----------------------------------------------------------------------
        // Calculate Remaining Days
        //----------------------------------------------------------------------
        if (dtBirthDate.Day > dtReferralDate.Day)
            //Logic: Figure out the days in month previous to the current month, or the admitted month.
            //       Subtract the birthday from the total days which will give us how many days the person has lived since their birthdate day the previous month.
            //       then take the referral date and simply add the number of days the person has lived this month.

            //If referral date is january, we need to go back to the following year's December to get the days in that month.
            if (dtReferralDate.Month == 1)
                iDays = DateTime.DaysInMonth(dtReferralDate.Year - 1, 12) - dtBirthDate.Day + dtReferralDate.Day;       
            else
                iDays = DateTime.DaysInMonth(dtReferralDate.Year, dtReferralDate.Month - 1) - dtBirthDate.Day + dtReferralDate.Day;       
        else
            iDays = dtReferralDate.Day - dtBirthDate.Day;             

        //----------------------------------------------------------------------
        // Store Days in Return Value
        //----------------------------------------------------------------------
        dYMD.Add("Days", iDays);

        return dYMD;
}



次のアプローチ(.NETクラスDateDiffのTime Period Libraryから抽出)では、カルチャ情報のカレンダーが考慮されます

// ----------------------------------------------------------------------
private static int YearDiff( DateTime date1, DateTime date2 )
{
  return YearDiff( date1, date2, DateTimeFormatInfo.CurrentInfo.Calendar );
} // YearDiff

// ----------------------------------------------------------------------
private static int YearDiff( DateTime date1, DateTime date2, Calendar calendar )
{
  if ( date1.Equals( date2 ) )
  {
    return 0;
  }

  int year1 = calendar.GetYear( date1 );
  int month1 = calendar.GetMonth( date1 );
  int year2 = calendar.GetYear( date2 );
  int month2 = calendar.GetMonth( date2 );

  // find the the day to compare
  int compareDay = date2.Day;
  int compareDaysPerMonth = calendar.GetDaysInMonth( year1, month1 );
  if ( compareDay > compareDaysPerMonth )
  {
    compareDay = compareDaysPerMonth;
  }

  // build the compare date
  DateTime compareDate = new DateTime( year1, month2, compareDay,
    date2.Hour, date2.Minute, date2.Second, date2.Millisecond );
  if ( date2 > date1 )
  {
    if ( compareDate < date1 )
    {
      compareDate = compareDate.AddYears( 1 );
    }
  }
  else
  {
    if ( compareDate > date1 )
    {
      compareDate = compareDate.AddYears( -1 );
    }
  }
  return year2 - calendar.GetYear( compareDate );
} // YearDiff

使用法:

// ----------------------------------------------------------------------
public void CalculateAgeSamples()
{
  PrintAge( new DateTime( 2000, 02, 29 ), new DateTime( 2009, 02, 28 ) );
  // > Birthdate=29.02.2000, Age at 28.02.2009 is 8 years
  PrintAge( new DateTime( 2000, 02, 29 ), new DateTime( 2012, 02, 28 ) );
  // > Birthdate=29.02.2000, Age at 28.02.2012 is 11 years
} // CalculateAgeSamples

// ----------------------------------------------------------------------
public void PrintAge( DateTime birthDate, DateTime moment )
{
  Console.WriteLine( "Birthdate={0:d}, Age at {1:d} is {2} years", birthDate, moment, YearDiff( birthDate, moment ) );
} // PrintAge



これはここで使用するバージョンです。 それは動作し、それはかなり簡単です。 それはJeffと同じ考えですが、私はそれが論理を分けて論理を分けるので少しはっきりしていると思うので、少し理解しやすくなります。

public static int GetAge(this DateTime dateOfBirth, DateTime dateAsAt)
{
    return dateAsAt.Year - dateOfBirth.Year - (dateOfBirth.DayOfYear < dateAsAt.DayOfYear ? 0 : 1);
}

そのようなことがはっきりしないと思えば、三元演算子をさらに拡張してより明確にすることができます。

明らかに、これはDateTime拡張メソッドとして行われますが、作業を行い、どこにでも配置できるコードの1行を取得できます。 ここでは、完全性のために、 DateTime.Nowに渡すExtensionメソッドの別のオーバーロードがあります。




私が今までに見つけた最も簡単な方法はこれです。 これは、米国と西ヨーロッパのロケールで正しく動作します。 他のロケール、特に中国のような場所に話すことはできません。 4つの余分な比較は、多くても、年齢の初期計算に従う。

public int AgeInYears(DateTime birthDate, DateTime referenceDate)
{
  Debug.Assert(referenceDate >= birthDate, 
               "birth date must be on or prior to the reference date");

  DateTime birth = birthDate.Date;
  DateTime reference = referenceDate.Date;
  int years = (reference.Year - birth.Year);

  //
  // an offset of -1 is applied if the birth date has 
  // not yet occurred in the current year.
  //
  if (reference.Month > birth.Month);
  else if (reference.Month < birth.Month) 
    --years;
  else // in birth month
  {
    if (reference.Day < birth.Day)
      --years;
  }

  return years ;
}

I was looking over the answers to this and noticed that nobody has made reference to regulatory/legal implications of leap day births. For instance, per Wikipedia , if you're born on February 29th in various jurisdictions, you're non-leap year birthday varies:

  • In the United Kingdom and Hong Kong: it's the ordinal day of the year, so the next day, March 1st is your birthday.
  • In New Zealand: it's the previous day, February 28th for the purposes of driver licencing, and March 1st for other purposes.
  • Taiwan: it's February 28th.

And as near as I can tell, in the US, the statutes are silent on the matter, leaving it up to the common law and to how various regulatory bodies define things in their regulations.

To that end, an improvement:

public enum LeapDayRule
{
  OrdinalDay     = 1 ,
  LastDayOfMonth = 2 ,
}

static int ComputeAgeInYears(DateTime birth, DateTime reference, LeapYearBirthdayRule ruleInEffect)
{
  bool isLeapYearBirthday = CultureInfo.CurrentCulture.Calendar.IsLeapDay(birth.Year, birth.Month, birth.Day);
  DateTime cutoff;

  if (isLeapYearBirthday && !DateTime.IsLeapYear(reference.Year))
  {
    switch (ruleInEffect)
    {
      case LeapDayRule.OrdinalDay:
        cutoff = new DateTime(reference.Year, 1, 1)
                             .AddDays(birth.DayOfYear - 1);
        break;

      case LeapDayRule.LastDayOfMonth:
        cutoff = new DateTime(reference.Year, birth.Month, 1)
                             .AddMonths(1)
                             .AddDays(-1);
        break;

      default:
        throw new InvalidOperationException();
    }
  }
  else
  {
    cutoff = new DateTime(reference.Year, birth.Month, birth.Day);
  }

  int age = (reference.Year - birth.Year) + (reference >= cutoff ? 0 : -1);
  return age < 0 ? 0 : age;
}

It should be noted that this code assumes:

  • A western (European) reckoning of age, and
  • A calendar, like the Gregorian calendar that inserts a single leap day at the end of a month.



I have a customized method to calculate age, plus a bonus validation message just in case it helps:

public void GetAge(DateTime dob, DateTime now, out int years, out int months, out int days)
{
    years = 0;
    months = 0;
    days = 0;

    DateTime tmpdob = new DateTime(dob.Year, dob.Month, 1);
    DateTime tmpnow = new DateTime(now.Year, now.Month, 1);

    while (tmpdob.AddYears(years).AddMonths(months) < tmpnow)
    {
        months++;
        if (months > 12)
        {
            years++;
            months = months - 12;
        }
    }

    if (now.Day >= dob.Day)
        days = days + now.Day - dob.Day;
    else
    {
        months--;
        if (months < 0)
        {
            years--;
            months = months + 12;
        }
        days += DateTime.DaysInMonth(now.AddMonths(-1).Year, now.AddMonths(-1).Month) + now.Day - dob.Day;
    }

    if (DateTime.IsLeapYear(dob.Year) && dob.Month == 2 && dob.Day == 29 && now >= new DateTime(now.Year, 3, 1))
        days++;

}   

private string ValidateDate(DateTime dob) //This method will validate the date
{
    int Years = 0; int Months = 0; int Days = 0;

    GetAge(dob, DateTime.Now, out Years, out Months, out Days);

    if (Years < 18)
        message =  Years + " is too young. Please try again on your 18th birthday.";
    else if (Years >= 65)
        message = Years + " is too old. Date of Birth must not be 65 or older.";
    else
        return null; //Denotes validation passed
}

Method call here and pass out datetime value (MM/dd/yyyy if server set to USA locale). Replace this with anything a messagebox or any container to display:

DateTime dob = DateTime.Parse("03/10/1982");  

string message = ValidateDate(dob);

lbldatemessage.Visible = !StringIsNullOrWhitespace(message);
lbldatemessage.Text = message ?? ""; //Ternary if message is null then default to empty string

Remember you can format the message any way you like.




This is not a direct answer, but more of a philosophical reasoning about the problem at hand from a quasi-scientific point of view.

I would argue that the question does not specify the unit nor culture in which to measure age, most answers seem to assume an integer annual representation. The SI-unit for time is second , ergo the correct generic answer should be (of course assuming normalized DateTime and taking no regard whatsoever to relativistic effects):

var lifeInSeconds = (DateTime.Now.Ticks - then.Ticks)/TickFactor;

In the Christian way of calculating age in years:

var then = ... // Then, in this case the birthday
var now = DateTime.UtcNow;
int age = now.Year - then.Year;
if (now.AddYears(-age) < then) age--;

In finance there is a similar problem when calculating something often referred to as the Day Count Fraction , which roughly is a number of years for a given period. And the age issue is really a time measuring issue.

Example for the actual/actual (counting all days "correctly") convention:

DateTime start, end = .... // Whatever, assume start is before end

double startYearContribution = 1 - (double) start.DayOfYear / (double) (DateTime.IsLeapYear(start.Year) ? 366 : 365);
double endYearContribution = (double)end.DayOfYear / (double)(DateTime.IsLeapYear(end.Year) ? 366 : 365);
double middleContribution = (double) (end.Year - start.Year - 1);

double DCF = startYearContribution + endYearContribution + middleContribution;

Another quite common way to measure time generally is by "serializing" (the dude who named this date convention must seriously have been trippin'):

DateTime start, end = .... // Whatever, assume start is before end
int days = (end - start).Days;

I wonder how long we have to go before a relativistic age in seconds becomes more useful than the rough approximation of earth-around-sun-cycles during one's lifetime so far :) Or in other words, when a period must be given a location or a function representing motion for itself to be valid :)




私のおすすめ

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

それは正しい日に年が変わるようです。 (私は107歳まで検査を受けました)




私はこれまでの回答のどれも、年齢を別々に計算する文化を提供していないと思います。 例えば、 東アジア時代と東アジア時代との比較を見てください。

実際の答えには、ローカリゼーションが含まれている必要があります。 この例では、 Strategy Patternがおそらく順番に並んでいます。




2解決すべき主な問題は次のとおりです。

1.正確な年齢の計算 - 年、月、日など

2.一般的に知覚される年齢を計算します。人々は通常、どれくらいの年齢を気にせず、今年の誕生日が気になるときだけ気にします。

1の解決策は明らかです。

DateTime birth = DateTime.Parse("1.1.2000");
DateTime today = DateTime.Today;     //we usually don't care about birth time
TimeSpan age = today - birth;        //.NET FCL should guarantee this as precise
double ageInDays = age.TotalDays;    //total number of days ... also precise
double daysInYear = 365.2425;        //statistical value for 400 years
double ageInYears = ageInDays / daysInYear;  //can be shifted ... not so precise

2の解は、全年齢を決定する際にそれほど正確ではないが、人々によって正確であると知覚されるものである。 人々は、通常、年齢を「手動で」計算すると、それを使用します。

DateTime birth = DateTime.Parse("1.1.2000");
DateTime today = DateTime.Today;
int age = today.Year - birth.Year;    //people perceive their age in years

if (today.Month < birth.Month ||
   ((today.Month == birth.Month) && (today.Day < birth.Day)))
{
  age--;  //birthday in current year not yet reached, we are 1 year younger ;)
          //+ no birthday for 29.2. guys ... sorry, just wrong date for birth
}

2への注記:

  • これは私が推奨する解決策です
  • 私たちは、うるう年の日数をシフトするので、DateTime.DayOfYearまたはTimeSpansを使用することはできません
  • 私は読みやすさのために少しだけ行を追加しました

もう1つのメモ...私は2つの静的なオーバーロードされたメソッドを作成します.1つは汎用的な使い方、もう1つは使い勝手の良さです。

public static int GetAge(DateTime bithDay, DateTime today) 
{ 
  //chosen solution method body
}

public static int GetAge(DateTime birthDay) 
{ 
  return GetAge(birthDay, DateTime.Now);
}



うるう年とすべてのために私が知っている最良の方法は次のとおりです。

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

お役に立てれば。




私はこれを使う:

public static class DateTimeExtensions
{
    public static int Age(this DateTime birthDate)
    {
        return Age(birthDate, DateTime.Now);
    }

    public static int Age(this DateTime birthDate, DateTime offsetDate)
    {
        int result=0;
        result = offsetDate.Year - birthDate.Year;

        if (offsetDate.DayOfYear < birthDate.DayOfYear)
        {
              result--;
        }

        return result;
    }
}



Here's yet another answer:

public static int AgeInYears(DateTime birthday, DateTime today)
{
    return ((today.Year - birthday.Year) * 372 + (today.Month - birthday.Month) * 31 + (today.Day - birthday.Day)) / 372;
}

This has been extensively unit-tested. It does look a bit "magic". The number 372 is the number of days there would be in a year if every month had 31 days.

The explanation of why it works ( lifted from here ) is:

Let's set Yn = DateTime.Now.Year, Yb = birthday.Year, Mn = DateTime.Now.Month, Mb = birthday.Month, Dn = DateTime.Now.Day, Db = birthday.Day

age = Yn - Yb + (31*(Mn - Mb) + (Dn - Db)) / 372

We know that what we need is either Yn-Yb if the date has already been reached, Yn-Yb-1 if it has not.

a) If Mn<Mb , we have -341 <= 31*(Mn-Mb) <= -31 and -30 <= Dn-Db <= 30

-371 <= 31*(Mn - Mb) + (Dn - Db) <= -1

With integer division

(31*(Mn - Mb) + (Dn - Db)) / 372 = -1

b) If Mn=Mb and Dn<Db , we have 31*(Mn - Mb) = 0 and -30 <= Dn-Db <= -1

With integer division, again

(31*(Mn - Mb) + (Dn - Db)) / 372 = -1

c) If Mn>Mb , we have 31 <= 31*(Mn-Mb) <= 341 and -30 <= Dn-Db <= 30

1 <= 31*(Mn - Mb) + (Dn - Db) <= 371

With integer division

(31*(Mn - Mb) + (Dn - Db)) / 372 = 0

d) If Mn=Mb and Dn>Db , we have 31*(Mn - Mb) = 0 and 1 <= Dn-Db <= 3 0

With integer division, again

(31*(Mn - Mb) + (Dn - Db)) / 372 = 0

e) If Mn=Mb and Dn=Db , we have 31*(Mn - Mb) + Dn-Db = 0

and therefore (31*(Mn - Mb) + (Dn - Db)) / 372 = 0




Links