Date difference in years using C

Question

How can I calculate date difference between two dates in years   For example   Datetime Now Today   - 11 03 2007  in years

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I implemented an extension method to get the number of years between two dates  rounded by whole months            lt summary gt          Gets the total number of years between two dates  rounded to whole months          Examples           2011-12-14  2012-12-15 returns 1          2011-12-14  2012-12-14 returns 1          2011-12-14  2012-12-13 returns 0 9167           lt  summary gt           lt param name  start  gt          Stardate of time period          lt  param gt           lt param name  end  gt          Enddate of time period          lt  param gt           lt returns gt          Total Years between the two days          lt  returns gt      public static double DifferenceTotalYears this DateTime start  DateTime end                   Get difference in total months          int months     end Year - start Year    12     end Month - start Month               substract 1 month if end month is not completed         if  end Day  lt  start Day                        months--                     double totalyears   months   12d          return totalyears

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If you need it for knowing someone s age for trivial reasons then Timespan is OK but if you need for calculating superannuation  long term deposits or anything else for financial  scientific or legal purposes then I m afraid Timespan won t be accurate enough because Timespan assumes that every year has the same number of days  same   of hours and same   of seconds    In reality the length of some years will vary  for different reasons that are outside the scope of this answer   To get around Timespan s limitation then you can mimic what Excel does which is       public int GetDifferenceInYears DateTime startDate  DateTime endDate                  Excel documentation says  COMPLETE calendar years in between dates          int years   endDate Year - startDate Year           if  startDate Month    endDate Month  amp  amp    if the start month and the end month are the same             endDate Day  lt  startDate Day   AND the end day is less than the start day                endDate Month  lt  startDate Month    OR if the end month is less than the start month                       years--                     return years

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Use   int Years DateTime start  DateTime end        return  end Year - start Year - 1               end Month  gt  start Month               end Month    start Month   amp  amp   end Day  gt   start Day      1   0

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Maybe this will be helpful for answering the question  Count of days in given year   new DateTime anyDate Year  12  31  DayOfYear   will include leap years too   Regarding DateTime DayOfYear Property

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Simple solution   public int getYearDiff DateTime startDate  DateTime endDate       int y   Year endDate  - Year startDate       int startMonth   Month startDate       int endMonth   Month endDate       if  endMonth  lt  startMonth           return y - 1      if  endMonth  gt  startMonth           return y      return  Day endDate   lt  Day startDate    y - 1   y

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var totalYears         DateTime Today - new DateTime 2007  03  11   TotalDays       365 2425    Average days from Wikipedia Leap year

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I have written an implementation that properly works with dates exactly one year apart   However  it does not gracefully handle negative timespans  unlike the other algorithm  It also doesn t use its own date arithmetic  instead relying upon the standard library for that   So without further ado  here is the code   DateTime zeroTime   new DateTime 1  1  1    DateTime a   new DateTime 2007  1  1   DateTime b   new DateTime 2008  1  1    TimeSpan span   b - a     Because we start at year 1 for the Gregorian    calendar  we must subtract a year here  int years    zeroTime   span  Year - 1      1  where my other algorithm resulted in 0  Console WriteLine  Yrs elapsed      years

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DateTime musteriDogum   new DateTime dogumYil  dogumAy  dogumGun    int additionalDays     DateTime Now Year - dogumYil    4     Count of the years with 366 days  int extraDays   additionalDays     DateTime Now Year   4    0    musteriDogum Year   4    0    1   0     We add 1 if this year or year inserted has 366 days  int yearsOld     DateTime Now - musteriDogum  Days - extraDays     365     Now we extract these extra days from total days and we can divide to 365

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I hope the link below helps  MSDN - DateTime Subtract Method  DateTime   There s even examples for C  there  Just simply click the C  language tab   Good luck

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Here is a neat trick which lets the system deal with leap years automagically   It gives an accurate answer for all date combinations   DateTime dt1   new DateTime 1987  9  23  13  12  12  0   DateTime dt2   new DateTime 2007  6  15  16  25  46  0    DateTime tmp   dt1  int years   -1  while  tmp  lt  dt2        years        tmp   tmp AddYears 1      Console WriteLine   0    years

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public string GetAgeText DateTime birthDate                const double ApproxDaysPerMonth   30 4375          const double ApproxDaysPerYear   365 25           int iDays    DateTime Now - birthDate  Days           int iYear    int  iDays   ApproxDaysPerYear           iDays -   int  iYear   ApproxDaysPerYear            int iMonths    int  iDays   ApproxDaysPerMonth           iDays -   int  iMonths   ApproxDaysPerMonth            return string Format   0    r   1  m  neder   2  dage   iYear  iMonths  iDays

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We had to code a check to establish if the difference between two dates  a start and end date was greater than 2 years   Thanks to the tips above it was done as follows    DateTime StartDate   Convert ToDateTime  01 01 2012     DateTime EndDate   Convert ToDateTime  01 01 2014     DateTime TwoYears   StartDate AddYears 2     if EndDate  gt  TwoYears

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This is the best code to calculate year and month difference   DateTime firstDate   DateTime Parse  1 31 2019    DateTime secondDate   DateTime Parse  2 1 2016     int totalYears   firstDate Year - secondDate Year  int totalMonths   0   if  firstDate Month  gt  secondDate Month      totalMonths   firstDate Month - secondDate Month  else if  firstDate Month  lt  secondDate Month        totalYears -  1      int monthDifference   secondDate Month - firstDate Month      totalMonths   12 - monthDifference     if   firstDate Day - secondDate Day     30        totalMonths    1      if  totalMonths   12    0                totalYears    1          totalMonths   0

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The following is based off Dana s simple code which produces the correct answer in most cases  But it did not take in to account less than a year between dates  So here is the code that I use to produce consistent results   public static int DateDiffYears DateTime startDate  DateTime endDate        var yr   endDate Year - startDate Year - 1                 endDate Month  gt   startDate Month  amp  amp  endDate Day  gt   startDate Day   1   0       return yr  lt  0   0   yr

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It s unclear how you want to handle fractional years  but perhaps like this   DateTime now   DateTime Now  DateTime origin   new DateTime 2007  11  3   int calendar years   now Year - origin Year  int whole years   calendar years -   now AddYears -calendar years   gt   origin   0  1   int another method   calendar years -   now Month - origin Month    32  gt   origin Day - now Day   0  1

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If you re dealing with months and years you need something that knows how many days each month has and which years are leap years   Enter the Gregorian Calendar  and other culture-specific Calendar implementations    While Calendar doesn t provide methods to directly calculate the difference between two points in time  it does have methods such as   DateTime AddWeeks DateTime time  int weeks  DateTime AddMonths DateTime time  int months  DateTime AddYears DateTime time  int years

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Works perfect       internal static int GetDifferenceInYears DateTime startDate                int finalResult   0           const int DaysInYear   365           DateTime endDate   DateTime Now           TimeSpan timeSpan   endDate - startDate           if  timeSpan TotalDays  gt  365                        finalResult    int Math Round  timeSpan TotalDays   DaysInYear   MidpointRounding ToEven                      return finalResult

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I found this at TimeSpan for years  months and days   DateTime target dob   THE DOB  DateTime true age   DateTime MinValue     TimeSpan  DateTime Now - target dob        Minimum value as 1 1 1 int yr   true age Year - 1

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int Age   new DateTime  DateTime Now - BirthDateTime  Ticks  Year   To calculate the elapsed years  age   the result will be minus one  var timeSpan   DateTime Now - birthDateTime  int age   new DateTime timeSpan Ticks  Year - 1

[c#] Date difference in years using C#

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