The Unix time stamp, which is commonly used, is calculated by counting the total seconds from the Unix Epoch on January 1st, 1970. But why? And in SAS software the system date is calculated by using 1st, 1960. Any interesting stories?
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5 Answers
Rather
say: "Why not?" Computer date/time entities fall into two groups:
those which are a count from an arbitrary date, and those that are
stored in some form as explicit dates (in some cases, as text).
But even those are arbitrary - they're referencing a date system that not all the world utilises.
Note that it's possible to represent a date older than this in Unix systems, it's just not possible to have a timestamp older than this. But as there weren't any Unix systems before that, such a timestamp would have no utility. They could have used the year 1900 as a baseline, but that would have, at a stroke, removed a vast range of timestamp values from any possible use - and there's already the issue of a 32-bit value rolling over in the next decade or so. Fortunately, it seems likely that everything will be 64-bit by then, apart from some embedded devices, perhaps - and they'll just have to go a double-word.
But even those are arbitrary - they're referencing a date system that not all the world utilises.
Note that it's possible to represent a date older than this in Unix systems, it's just not possible to have a timestamp older than this. But as there weren't any Unix systems before that, such a timestamp would have no utility. They could have used the year 1900 as a baseline, but that would have, at a stroke, removed a vast range of timestamp values from any possible use - and there's already the issue of a 32-bit value rolling over in the next decade or so. Fortunately, it seems likely that everything will be 64-bit by then, apart from some embedded devices, perhaps - and they'll just have to go a double-word.
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