There's a language out there called "Progress Advanced Business Language" (or "Open Edge Advanced Business Language"). Just hearing that string of words in a sequence tells you you're in for it. It's a verbose, "English-like" programming language. But we're not here to pick on the language.

A long time ago, Mirjam had the "pleasure" of working in a Progress ABL environment. At some point, one of the developers had needed to find a date six months prior to the current date. It didn't need to be accurate, and thus said developer littered the code with comments reminding everyone that it didn't need to be that accurate. They arguably spent more time defending the choice to be inaccurate than it would have taken to write code that would have been accurate.

Mirjam doesn't have the code anymore, so what we have here is a mix of her remembered pseudocode, Progress syntax, and my attempts to clarify all of it. Let's not worry too much about the language, and instead focus on the logic:

ASSIGN v-date = TODAY.

/* Calculates the current week/year */
RUN week.p(INPUT v-date, OUTPUT v-weeknumber, OUTPUT v-year).

IF v-weeknumber > 26 THEN 
    ASSIGN v-weeknumber = v-weeknumber - 26.
ELSE 
    ASSIGN v-weeknumber = 52 - 26 - v-weeknumber
           v-year       = v-year - 1.

/* Turn the result of that calculation back into a date */
RUN week2.p(INPUT v-weeknumber, INPUT v-year, OUTPUT v-resultdate).

This code gets the current date. It then breaks that into week number of the date (1-52), and the year of the date. Then, if the week number is greater than 26, it subtracts 26 from it, giving us a date half a year ago, ish. If the current weak number is less than or equal to 26, we do 52 - 26 - v-weeknumber, and decrement the year. Which yes, is a fairly round about way to handle the rollover- 52 - 26 happens to be… 26.

It's worth noting, that as primitive looking as this syntax is, Progress ABL does have an ADD_INTERVAL function, which lets you do date arithmetic, without all this nonsense. In fact, Mirjam went ahead and replaced all of this with a single line.

That said, as a little bonus WTF, Progress does have some weird date quirks, for example, you can construct a date from an integer. Which has a very unsurprising (but also, weirdly surprising) range of possible values:

The value of the expression cannot be a date value before 12/31/-32768 or after 12/31/32767.

At least that covers a range that includes both the discovery of agriculture and the eventual rediscovery of agriculture after the event that enters into legend as "The Fall".

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