Why did COBOL code become important during the Y2K problem?

COBOL became central to the Y2K problem because it was the primary programming language used for decades by large organizations, such as banks and government agencies, to manage massive amounts of business data.12

In the early days of computing, programmers frequently abbreviated four-digit years to two digits to conserve memory space. Because COBOL was the standard language for these critical mainframe systems, a vast amount of legacy code relied on this two-digit date format. As the year 2000 approached, there was widespread concern that these systems would interpret "00" as 1900 rather than 2000, leading to catastrophic failures in financial, utility, and government records. Consequently, the Y2K-compliance effort required a massive, intensive review and correction of this existing COBOL code to ensure systems could correctly process the transition to the new millennium.31