No, COBOL does not inherently default to 1875-05-20 for corrupt or missing dates. The appearance of this specific date likely stems from particular implementations or custom error handling within specific COBOL systems. The language itself doesn't prescribe this default. Instead, how COBOL handles invalid dates depends on the compiler, runtime environment, and how the program was written. A program might display a default value, a blank date, or trigger an error message, among other possibilities. The 1875-05-20 date is potentially an arbitrary choice made by a programmer or a consequence of how a specific system interprets corrupted data.
The blog post explores optimizing date and time calculations in Python by creating custom algorithms tailored to specific needs. Instead of relying on general-purpose libraries, the author develops optimized functions for tasks like determining the day of the week, calculating durations, and handling recurring events. These algorithms, often using bitwise operations and precomputed tables, significantly outperform standard library approaches, particularly when dealing with large numbers of calculations or limited computational resources. The examples demonstrate substantial performance improvements, highlighting the potential gains from crafting specialized calendrical algorithms for performance-critical applications.
Hacker News users generally praised the author's deep dive into calendar calculations and optimization. Several commenters appreciated the clear explanations and the novelty of the approach, finding the exploration of Zeller's congruence and its alternatives insightful. Some pointed out potential further optimizations or alternative algorithms, including bitwise operations and pre-calculated lookup tables, especially for handling non-proleptic Gregorian calendars. A few users highlighted the practical applications of such optimizations in performance-sensitive environments, while others simply enjoyed the intellectual exercise. Some discussion arose regarding code clarity versus performance, with commenters weighing in on the tradeoffs between readability and speed.
JavaScript's new Temporal API provides a modern, comprehensive, and consistent way to work with dates and times. It addresses the shortcomings of the built-in Date object with clear and well-defined types for instants, durations, time zones, and calendar systems. Temporal offers powerful features like easy date/time arithmetic, formatting, parsing, and manipulation, making complex time-related tasks significantly simpler and more reliable. The API is now stage 3, meaning its core functionalities are stable and are implemented in current browsers, paving the way for wider adoption and improved date/time handling in JavaScript applications.
Hacker News users generally expressed enthusiasm for the Temporal API, viewing it as a significant improvement over the problematic native Date object. Several commenters highlighted Temporal's immutability and clarity around time zones as major advantages. Some discussed the long and arduous process of getting Temporal standardized, acknowledging the efforts of the involved developers. A few users raised concerns, questioning the API's verbosity and the potential difficulties in migrating existing codebases. Others pointed out the need for better documentation and broader community adoption. Some comments touched upon specific features, such as the plain-date and plain-time objects, and compared Temporal to similar date/time libraries in other languages like Java and Python.
Summary of Comments ( 292 )
https://news.ycombinator.com/item?id=43073149
Hacker News users discuss various potential reasons for the 1875-05-20 default date in COBOL, with speculation centering around it being an arbitrary "filler" value chosen by programmers or a remnant of test data. Some commenters suggest it might relate to specific COBOL implementations or be a misinterpretation of a different default behavior, like zeroing out the date field. Others offer alternative explanations, proposing it could represent the earliest representable date in a particular system or stem from a known data corruption issue. A few emphasize the importance of context and specific COBOL versions, noting that the behavior isn't a universal standard. The overall tone suggests the specific date's origin is uncertain and likely varies depending on the system in question.
The Hacker News post titled "Does or did COBOL default to 1875-05-20 for corrupt or missing dates?" has several comments discussing the quirks of COBOL date handling.
One commenter shares an anecdote about encountering a similar issue with a COBOL system at a bank in the 1990s. The system used a default date of 1900-01-01 for bad dates, leading to incorrect interest calculations and frustrated customers. This personal experience adds weight to the idea of default dates causing real-world problems in COBOL systems.
Another commenter clarifies that COBOL itself doesn't have a built-in default date. Instead, the specific behavior depends entirely on how the individual program was written. They explain that the default date would be whatever the programmer coded it to be, or potentially a system-level default set by the operating system or runtime environment. This highlights the importance of understanding the specific implementation details of a COBOL system rather than assuming universal behavior.
Expanding on the programming aspect, a subsequent comment mentions the common practice of using
LOW-VALUESas a placeholder for missing or invalid dates.LOW-VALUESis not a specific date, but rather a special value representing the lowest possible value for a data field. This points to a common technique used by COBOL programmers to handle data integrity issues.One comment humorously suggests the possibility of the 1875-05-20 date being a programmer's birthday or another significant date, but acknowledges this is pure speculation. This adds a touch of levity to the discussion while hinting at the mysteries that can lurk within legacy code.
Another commenter, with apparent experience in COBOL systems, questions the validity of the 1875 date. They point out the relative recency of COBOL compared to that date, suggesting it's unlikely to be a genuine default. They posit that it's more probable the date arose from a specific data corruption incident rather than a deliberate design choice.
Finally, a comment discusses how default dates in older systems could sometimes reflect the earliest date representable in a given data format. This offers a technical explanation for how unusual default dates might arise, even without explicit programmer intervention. They explain how systems relying on two-digit year representations could end up interpreting "00" as 1900 or even 1800.
In summary, the comments paint a picture of COBOL date handling as being highly dependent on specific implementations. While COBOL itself doesn't dictate a default date, a variety of practices and potential errors could lead to unexpected results. The discussion moves from personal anecdotes and speculation to more technical explanations of how and why unusual default dates might appear in these systems.