[HECnet] The new few centuries (or DATE75)

[Thomas DeBellis]

Oh you mean the 'orange' book?  Yeah, they were great.

Your observation that not all months have 31 days is, of course, 
correct.  I think what it's telling me is that DATE75 is /not/ the 
monitor internal format, but rather a method of encoding and conveying 
the current date.  Explicit, the monitor is never going to have the DATE 
UUO give February 30^th and 31^st and maybe not the 29^th .  It would be 
worth a look if you know what module it's in (I don't have Tops-10 sources).

Internally, Tops-10 is likely maintaining two clocks, a JIFFY based 
uptime counter and a time of day based on 18 bits of a day count from 
1858 and eighteen bits of a fixed fraction of day/(2^^18 ), which yields 
a resolution of about ⅓ of a second.

Tops-10 is almost the same except that it uses milliseconds as an uptime 
counter.
> ------------------------------------------------------------------------
> On 12/31/20 6:14 PM, Robert Armstrong wrote:
>
>    Yeah, but the arithmetic doesn't work out.  Between 1/1/64 and 1/4/75 are only 4021 days.
>
>    Hmmm - 31 days * 12 months * 11 years = 4092...  That works out about right for 1/4/75.
>
>    The date calculation must have assumed that there were 31 days in all months.
>
>    I should dig out my old TOPS-10 "telephone book" reference manual and see what it says...
>
> Bob
>> ------------------------------------------------------------------------
>> On 12/31/20 6:05 PM, Thomas DeBellis wrote:
>>
>> For 12 bits, the largest date comes out to 1/4/1975
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