[Info-vax] Significance of 2020 / 2021 date

[Stephen Hoffman]

On 2021-01-07 18:39:59 +0000, Simon Clubley said:

> On 2021-01-07, Andy Burns <usenet at andyburns.uk> wrote:
>> issinoho wrote:
>> 
>>> We have some old 90s VAX C code which rejects any dates after the year 2020
>> 
>> Does this use 2 digit years or 4 digit?
>> 
>> Some systems use "date windowing" and assume e.g. yy below 20 means 
>> 19yy otherwise it means 20yy.
> 
> That's exactly what I thought when I saw the date but I would have 
> expected the check to be for less than 1-Jan-2020 instead of 1-Jan-2021 
> unless someone decided to be different.

Lots of possibilities.

Have a look at the C code.

Or have somebody look at the C code on your behalf.

Non-leap-year years that begin on Thursday and leap-year years that 
begin on Wednesday have 53 weeks.

Which can snarl some applications.

2020 was one such year; with 53 weeks.

Wouldn't be surprised if that triggered a fault somewhere in week-based code.

Migrating from K&R to ANSI C and fixing diagnostics has stabilized a 
whole lot of sketchy old apps, too.



-- 
Pure Personal Opinion | HoffmanLabs LLC