Discussion:
Remembering the HP-2000/A timeshare midnight rollover
Add Reply
David LaRue
2020-12-31 13:21:01 UTC
Reply
Permalink
Hello,

During High School we had access to an HP-2000/Access timeshare system. I
found that the system time wrapped oddly on New Year. It rolled over to
December 32 of the same year. The System Operator had to manually update
the date at the start of the new year.

Were there other systems that didn't handle December to January rollovers?

Happy 2021 everyone!
Charlie Gibbs
2020-12-31 19:03:41 UTC
Reply
Permalink
Post by David LaRue
Hello,
During High School we had access to an HP-2000/Access timeshare system. I
found that the system time wrapped oddly on New Year. It rolled over to
December 32 of the same year. The System Operator had to manually update
the date at the start of the new year.
Were there other systems that didn't handle December to January rollovers?
Hell, early versions of MS-DOS didn't even handle midnight rollover
reliably. A 10-line BASIC program that shows date and time whenever
either one changes would produce output with various combinations of
some, all, or none of the following, depending on version, machine,
and probably phase of the moon:

12-24-1985 23:59:58
12-24-1985 23:59:59
12-24-1985 24:00:00
12-24-1985 00:00:00
12-25-1985 00:00:00
12-25-1985 00:00:01

Been there, done that, wrote nasty code to deal with it.

Fred Brooks, in _The Mythical Man-Month_, describes the decision to
omit code that handled February 29 in leap years, to save 100 bytes.
Post by David LaRue
Happy 2021 everyone!
Same to you.
--
/~\ Charlie Gibbs | "Some of you may die,
\ / <***@kltpzyxm.invalid> | but it's a sacrifice
X I'm really at ac.dekanfrus | I'm willing to make."
/ \ if you read it the right way. | -- Lord Farquaad (Shrek)
Kerr-Mudd,John
2021-01-07 21:56:41 UTC
Reply
Permalink
On Thu, 31 Dec 2020 19:03:41 GMT, Charlie Gibbs
Post by Charlie Gibbs
Post by David LaRue
Hello,
During High School we had access to an HP-2000/Access timeshare
system. I found that the system time wrapped oddly on New Year. It
rolled over to December 32 of the same year. The System Operator had
to manually update the date at the start of the new year.
Were there other systems that didn't handle December to January rollovers?
Hell, early versions of MS-DOS didn't even handle midnight rollover
reliably. A 10-line BASIC program that shows date and time whenever
either one changes would produce output with various combinations of
some, all, or none of the following, depending on version, machine,
12-24-1985 23:59:58
12-24-1985 23:59:59
12-24-1985 24:00:00
12-24-1985 00:00:00
12-25-1985 00:00:00
12-25-1985 00:00:01
Been there, done that, wrote nasty code to deal with it.
Fred Brooks, in _The Mythical Man-Month_, describes the decision to
omit code that handled February 29 in leap years, to save 100 bytes.
I tried searching for this and I got

https://chryss.eu/tag/software/
<Quote>
according to Brooks, who had been one of the the project’s managers in
the 1960s, a typical second system. And to support his claim that it was
overblown and wasteful, he offers this example:

For example, OS/360 devotes 26 bytes of the permanently resident date-
turnover routine to the proper handling of December 31 on leap years
(when it is Day 366). That might have been left to the operator.
</Quote>
Post by Charlie Gibbs
Post by David LaRue
Happy 2021 everyone!
Same to you.
--
Bah, and indeed, Humbug.
Loading...