[squeak-dev] UnixTime

Chris Muller asqueaker at gmail.com
Sun Nov 20 20:45:46 UTC 2016

I don't agree that the Squeak epoch was "supposed" to have been
defined relative to UTC.  Its just a number, it don't see that it
matters when or what number we start with, as long as it satisfies its
requirement of being a numerical representation, and we don't change
it.  Changing it would be breaking it for all applications which ever
used it.

On Sat, Nov 19, 2016 at 10:12 PM, David T. Lewis <lewis at mail.msen.com> wrote:
> On Fri, Nov 18, 2016 at 07:01:29PM +0100, Bert Freudenberg wrote:
>> On Fri, Nov 18, 2016 at 2:16 PM, Edgar De Cleene <edgardec2005 at gmail.com>
>> wrote:
>> > Fellows:
>> > I found useful add UnixTime at the beginning of file names for you have
>> > nnnFoo.etc what is compatible with different OS and you easily see ordered
>> > .
>> >
>> > But I my image I do not have how convert this value to DateAndTime again.
>> > So i attach this just in case some could use it.
>> >
>> Since we already have DateAndTime>>asUnixTime, having DateAndTime
>> class>>fromUnixTime: seems like a reasonable addition. Thank you!
>> - Bert -
> Edgar's enhancement looks good to me also, but unfortunately it does not
> work due to a problem in DateAndTime class>>fromSeconds:, which is supposed
> to do this:
>    DateAndTime class>>fromSeconds: seconds
>        "Answer a DateAndTime since the Squeak epoch: 1 January 1901"
> If we agree that the Squeak epoch was supposed to have been defined relative
> to UTC, then #fromSeconds: is broken because it treats its argument as
> seconds since the "local Squeak epoch" (early Squeak VMs were built upon
> the faulty premise of using local time).
> Because of this problem in #fromSeconds: we get the following (I am five
> hours from GMT):
>    dt1 := DateAndTime now.
>    unixSeconds1 := dt1 asUnixTime.
>    dt2 := DateAndTime fromUnixTime: unixSeconds1.
>    unixSeconds2 := dt2 asUnixTime.
>    dt2 - dt1. ==> 0:04:59:59.890588
>    unixSeconds2 - unixSeconds1. ==> 18000
> IMO, Edgar's method is correct and we should fix DateAndTime class>>fromSeconds:
> so that the argument is interpreted as seconds since the UTC Smalltalk epoch.
> <OT>
> Note also that #asUnixTime truncates (or rounds?) to a whole second, which is
> reasonable given that Unix time(2) does the same thing. But it might deserve
> a method comment if that is the intended behavior. If the method was named
> #asPosixTime, then I might argue that the value should not be rounded or
> truncated.
> </OT>
> Dave

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