It stands for year-two-kilo in Spanish year 2. 000 . It was a computer-type problem generated by programming errors. It is also known as millennium effect, effect 2. 000 , Millennium Error or Computer Error of the Year 2000 .
'Y2K' is the English number for year two kilo (year two kilo, year 2000) which was used to shorten the millennium error in computing.