[HECnet] The new few centuries (or DATE75)

[Robert Armstrong]

> 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.  

  Actually as I remember the rollover was sometime in March 1975, not January.

  The DATE75 patch squeezed out three extra bits in the directory structure to allow for 32,768 days since 1/1/64.

Bob