an error in the coding of certain computer programs in which the year portion of dates was represented by only two decimal digits, assuming that the first two digits are “19”. In such a program the the year 1975 is represented as “75”. This was a common practise in computer programming even into the 1990's, as many programmers failed to consider that their programs would be used after the year 1999. Thus, with such a program, a person born in 2000 would be considered as 101 years old in 2001; many different serious problems, as various as the programs, could be caused by such an error.