Military Origins

The term "D-Day" is military lingo. The "D" simply stands for "Day". It designates the start date of a combat operation. The day before is D-1, the day after is D+1.

The Most Famous D-Day

While used for many operations, the term is synonymous with June 6, 1944: The Allied invasion of Normandy during World War II (Operation Overlord).

Modern Usage

Today, "D-Day" is used casually to refer to any significant date:

• Exams (CSAT, SAT)
• Weddings
• Project Deadlines
• Anniversaries

Using a calculator helps manage the anxiety and excitement leading up to these big moments.