Re: [r6rs-discuss] [Scheme-reports] Date and time arithmetic library proposal for R7RS large Scheme

[John Cowan <cowan@x>]

Marc Feeley scripsit:

> The problem is that a "date" is just a label for a point in time.
> A label assigned by humans in a rather arbitrary way that can't
> even be determined ahead of time (leap seconds, time zones, etc).

Quite so, which is why I have both instants and date objects.

> It is quite a shock to think that our "date" labelling system isn't
> even one-to-one with time points (for example, on the US east coast,
> there are two points in time that correspond to 1:30 AM November 7,
> 2010, because at 2 AM November 7, 2010 the clocks are set back to 1
> AM to return to Standard Time).

Hence the existence of the daylight-savings-time field and its C analogue,
the dstflag.

> I want to make sure that the date and time abstractions are not
> hopelessly intertwined.  The thread/process scheduler of an OS should
> work with time points.  A calendar application should work with dates.

Correct.  And it's a calendar API I'm proposing.

-- 
John Cowan  cowan@x  http://ccil.org/~cowan
The penguin geeks is happy / As under the waves they lark
The closed-source geeks ain't happy / They sad cause they in the dark
But geeks in the dark is lucky / They in for a worser treat
One day when the Borg go belly-up / Guess who wind up on the street.

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