Converting a year from 4 digit to 2 digit and back again in C

Question

My credit card processor requires I send a two-digit year from the credit card expiration date  Here is how I am currently processing    I put a DropDownList of the 4-digit year on the page  I validate the expiration date in a DateTime field to be sure that the expiration date being passed to the CC processor isn t expired  I send a two-digit year to the CC processor  as required   I do this via a substring of the value from the year DDL    Is there a method out there to convert a four-digit year to a two-digit year  I am not seeing anything on the DateTime object  Or should I just keep processing it as I am

User · Answer

Here is a link to a 4Guys article on how you can format Dates and Times using the ToString() method by passing in a custom format string.

http://www.aspfaqs.com/aspfaqs/ShowFAQ.asp?FAQID=181

Just in case it goes away here is one of the examples.

'Create a var. named rightNow and set it to the current date/time
Dim rightNow as DateTime = DateTime.Now
Dim s as String 'create a string

s = rightNow.ToString("MMM dd, yyyy")

Since his link is broken here is a link to the DateTimeFormatInfo class that makes those formatting options possible.

http://msdn.microsoft.com/en-us/library/system.globalization.datetimeformatinfo.aspx

It's probably a little more consistent to do something like that rather than use a substring, but who knows.

User · Answer

I ve seen some systems decide that the cutoff is 75  75  is 19xx and below is 20xx

User · Answer

Even if a builtin way existed  it wouldn t validate it as greater than today and it would differ very little from a substring call  I wouldn t worry about it

User · Answer

This should work for you   public int Get4LetterYear int twoLetterYear        int firstTwoDigits           Convert ToInt32 DateTime Now Year ToString   Substring 2  2        return Get4LetterYear twoLetterYear  firstTwoDigits      public int Get4LetterYear int twoLetterYear  int firstTwoDigits        return Convert ToInt32 firstTwoDigits ToString     twoLetterYear ToString        public int Get2LetterYear int fourLetterYear        return Convert ToInt32 fourLetterYear ToString   Substring 2  2        I don t think there are any special built-in stuff in  NET   Update  It s missing some validation that you maybe should do  Validate length of inputted variables  and so on

User · Answer

The answer is quite simple   DateTime Today   DateTime Today  string zeroBased   Today ToString  yy-MM-dd

User · Answer

This seems to work okay for me  yourDateTime ToString   Substring 2

User · Answer

At this point  the simplest way is to just truncate the last two digits of the year   For credit cards  having a date in the past is unnecessary so Y2K has no meaning   The same applies for if somehow your code is still running in 90  years   I d go further and say that instead of using a drop down list  let the user type in the year themselves   This is a common way of doing it and most users can handle it

User · Answer

Use the DateTime object ToString with a custom format string like myDate ToString  MM dd yy    for example

User · Answer

This is an old post  but I thought I d give an example using an ExtensionMethod  since C  3 0   since this will hide the implementation and allow for use everywhere in the project instead or recreating the code over and over or needing to be aware of some utility class      Extension methods enable you to  add  methods to existing types   without creating a new derived type  recompiling  or otherwise   modifying the original type  Extension methods are a special kind of   static method  but they are called as if they were instance methods on   the extended type  For client code written in C  and Visual Basic    there is no apparent difference between calling an extension method   and the methods that are actually defined in a type    public static class DateTimeExtensions               public static int ToYearLastTwoDigit this DateTime date                        var temp   date ToString  yy                return int Parse temp                     You can then call this method anywhere you use a DateTime object  for example     var dateTime   new DateTime 2015  06  19   var year   cob ToYearLastTwoDigit

User · Answer

using java script var curDate   new Date    var curYear   curDate getFullYear    curYear   curYear toString   slice 2   document write curYear    using java script   using sqlserver select Right Year getDate    2    using sql server   Using c  net  DateTime dt   DateTime Now              string curYear   dt Year ToString   Substring 2 2  ToString        using c  net

User · Answer

Why not have the original drop down on the page be a 2 digit value only  Credit cards only cover a small span when looking at the year especially if the CC vendor only takes in 2 digits already

User · Answer

The answer is already given  But here I want to add something  Some person told that it did not work    May be you are using      DateTime Now Year ToString  yy      that is why it is not working  I also made the same the mistake   Change it to      DateTime Now ToString  yy

User · Answer

If you re creating a DateTime object using the expiration dates  month year   you can use ToString   on your DateTime variable like so   DateTime expirationDate   new DateTime 2008  1  31      random date string lastTwoDigitsOfYear   expirationDate ToString  yy      Edit  Be careful with your dates though if you use the DateTime object during validation  If somebody selects 05 2008 as their card s expiration date  it expires at the end of May  not on the first

User · Answer

1st solution  fastest     yourDateTime Year   100   2nd solution  more elegant in my opinion     yourDateTime ToString  yy

User · Answer

DateTime Now Year -  DateTime Now Year   100   100    Works for current year  Change DateTime Now Year to make it work also for another year

[c#] Converting a year from 4 digit to 2 digit and back again in C#

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