I thought a historical opportunity had passed me by, but a full decade after the turn of the millennium in 2010 I found my first Y2K bug! If you, like me, were working in eCommerce (who remembers that buzzword?) in the late 1990s and thought you missed your chance I'm here to tell you its still not too late. As long as you work for the right company with the enough legacy technology around you can still find a Y2K bug of your own!

What was going on?

I was writing a new Rails application on top of an old Oracle database. The database had a constraint

graduationdate BETWEEN TO_DATE('01-JAN-1900','DD-MON-YYYY') AND TO_DATE('31-DEC-2100','DD-MON-YYYY')

To me this looked like a basic check to make sure the date was within a 300 year range as a basic sanity-check. I implemented an ActiveRecord validation in my model

validate :validate_graduation_date
def validate_graduation_date
  unless graduationdate.nil?
    earliest_date, latest_date = Date.parse('01-JAN-1900'), Date.parse('31-DEC-2100')
    errors.add(:graduationdate, 'must be between 01-JAN-1900 and 31-DEC-2100') unless graduationdate > earliest_date and graduationdate < latest_date  
  end
end

Of course I had unit tests that all passed

describe 'graduation date' do
  it 'should not allow July 4, 1776' do
    education = Factory.build :education, :graduationdate=>Date.parse('04-JUL-1776')
    education.should_not be_valid
  end
  it 'should allow Aug 1 1970' do
    education = Factory.build :education, :graduationdate=>Date.parse('01-AUG-1970')
    education.should be_valid
  end
  it 'should allow Mar 15 2000' do
    education = Factory.build :education, :graduationdate=>Date.parse('15-MAR-2000')
    education.should be_valid
  end
  it 'should not allow Jan 1, 2525' do
    education = Factory.build :education, :graduationdate=>Date.parse('01-JAN-2525')
    education.should_not be_valid
  end
end

BUT once I went into production with my legacy database I started getting errors. So I took a look at one of the rows giving me an error and discovered the graduation date was 01-JAN-00. AHA a 2-digit year. That doesn't look good and there were over 100,000 rows with this problem.

select count(*) from education where graduationdate = to_date('01-jan-1900')
COUNT(*)               
---------------------- 
116232       

Once I realized that the database contained data for January 1st 1900 and I discovered the Oracle BETWEEN function is inclusive I was able to solve my problem by changing my ActiveRecord validation to have a >= and lt;=.

validate :validate_graduation_date
def validate_graduation_date
  unless graduationdate.nil?
    earliest_date, latest_date = Date.parse('01-JAN-1900'), Date.parse('31-DEC-2100')
    errors.add(:graduationdate, 'must be between 01-JAN-1900 and 31-DEC-2100') unless graduationdate >= earliest_date and graduationdate <= latest_date  
  end
end

I added some specs to test my boundary conditions

it 'should not allow Dec 31 1899' do
  education = Factory.build :education, :graduationdate=>Date.parse('31-DEC-1899')
  education.should_not be_valid
end
it 'should allow Jan 1 1900' do
  education = Factory.build :education, :graduationdate=>Date.parse('01-JAN-1900')
  education.should be_valid
end
it 'should allow Dec 31 2099' do
  education = Factory.build :education, :graduationdate=>Date.parse('31-DEC-2099')
  education.should be_valid
end
it 'should allow Jan 1 2100' do
  education = Factory.build :education, :graduationdate=>Date.parse('01-JAN-2100')
  education.should_not be_valid
end

So what's the moral?

I'm not sure but when you're have to integrate with a legacy system you should account for the absurd - in my case a job application from a candidate who graduated more than 100 years ago!

And if you feel like you missed out on a once-in-a-lifetime opportunity to work on Y2K bugs don't despair. They are still out there!