1 Jan
2021
1 Jan
'21
6:48 p.m.
On Dec 31, 2020, at 5:45 PM, Robert Armstrong <bob
at jfcl.com> wrote:
I thought maybe you meant the DOS-11 DECtape date problem, but that hit in 1974. The
reason is also 12 bits, and the fact that date is encoded (as it is on RSTS) as (year -
1970) * 1000 + day. So somewhere in April 1974 the date would wrap. Fixed, on RSTS at
least, by changing it to 15 bits, since the next higher 3 bits were unused on RSTS.
I was in college when this happened, and I remember diagnosing the issue and sending the
patch to DEC. :-)
paul
Thomas DeBellis wrote:
So I went spelunking and here is what DATE75 is all about.
Briefly, very early versions of Tops-10 could only handle dates between January 1st 1964
and January 4th 1975 ...
The DECtape directory format (on TOPS-10) used only 12 bits to store the date, and
between 1964 and 1975 are 4096 days.