You'll find long lines at automated teller machines. Technical support for most software applications might cease after today. Computer passwords expire and lock system administrators out of their systems. Incorrect bills are sent out. Manual paperwork begins.
Supply chains begin disruption.
The first Year-2000 casualties occur. Year-2000 litigation begins. The first business day of the Year-2000 in the United States of America. The first business day of the Year-2000 in the United Kingdom and the European Union. Some major software application packages don't know this date exists.