Why COBOL 1875? Understanding the Myth and the Truth Behind the Date Mystery 

If you’ve ever worked with COBOL or have spent time on programming forums, you’ve likely encountered the curious case of the “default date” in COBOL being set to May 20, 1875. This has been a subject of many debates and misconceptions, particularly in the wake of a disinformation campaign about the existence of 150-year-old individuals in the U.S. Social Security database. But is there any truth to this claim? Let’s break down the facts and separate myth from reality.  

The Myth: COBOL’s Default Date Is May 20, 1875

The story that has been circulating online suggests that when COBOL, a programming language created in the 1950s, encounters a missing or null date, it defaults to May 20, 1875. Some versions of this myth even claimed that this date is used as a placeholder in COBOL systems and that it has something to do with the Convention of the Meter, which was signed on May 20, 1875, marking the beginning of standardized measurements. 

This idea, while fascinating, is simply not true, and it’s important to understand why. 

The Truth: COBOL Doesn’t Have a “Default Date”

In reality, COBOL doesn’t have a “default date” or any built-in date data type. Dates in COBOL are not standardized in a way that would result in a system defaulting to any specific value like May 20, 1875. Instead, dates are typically stored as numeric or character strings, and it’s up to the programmer to define how they’re stored and managed. There’s no intrinsic behavior in COBOL that would automatically insert a specific date in the absence of one. 

Even if there were a “default” date, choosing May 20, 1875, would be an odd and arbitrary decision. COBOL’s flexibility allows developers to choose how to handle missing dates, and it’s common practice to use null values or flags like “9999-12-31” to represent unknown or invalid dates. 

The Origins of the Confusion 

 So where did the May 20, 1875, date come from? This is where things get interesting. The confusion likely arises from a historical reference in the ISO8601 standard, which governs date formats. In the 2004 edition of ISO8601, May 20, 1875, was mentioned in the context of the Gregorian calendar as the reference point for the date of the “Convention du Mètre” signed in Paris. This was a treaty that helped establish the metric system of measurements. 

However, this reference was not related to COBOL or any other programming language. It was simply an example used to explain the Gregorian calendar, and it was never intended to be used as a “default” date in software systems. In fact, this mention of 1875 was removed in the 2019 update to ISO8601

The Disinformation Spiral 

The myth took on a life of its own in 2025 when Elon Musk mentioned that some Social Security records showed people “150 years old.” The claim was quickly amplified by various individuals online, who inaccurately tied the idea of 150-year-olds to the erroneous assumption that COBOL was using May 20, 1875, as a default date for missing dates. 

This misinformation spread rapidly across social media, fueled by a mix of misunderstandings, misinformation, and a lack of technical knowledge on how COBOL handles dates. Despite numerous debunkings by experts, the myth persists in certain corners of the internet. 

How COBOL Actually Stores Dates 

In COBOL, dates are typically stored as numeric fields. For example, a six-character date field might store the date in the format YYMMDD, where YY represents the last two digits of the year, MM represents the month, and DD represents the day. For instance, January 25, 1987, would be stored as 870125. 

If you want to retrieve the current date in a COBOL program, you use the ACCEPT statement, which pulls the date from the system clock. If you’re working with a specific date format or need to handle missing or invalid dates, you’d define your own conventions — but again, there is no “default date” like May 20, 1875, lurking in the background. 

Conclusion: The Fallacy of COBOL’s Default Date

The notion that COBOL has a default date of May 20, 1875, is a product of misinformation and misunderstanding, perpetuated by a combination of historical references, disinformation campaigns, and a lack of knowledge about how COBOL handles dates. The truth is that COBOL doesn’t assign a default date to missing values, and the example of May 20, 1875, has no connection to COBOL’s internal workings. 

Understanding the realities of how COBOL stores and manages dates is crucial for anyone working with legacy systems. The important takeaway is that COBOL’s date handling is flexible and dependent on the programmer’s decisions, rather than some mysterious default value tied to an obscure historical event.