[go-nuts] What's wrong with time package?

It seems to work as it should ( fmt.Println(t.Format("Jan 2, 2006")) is the
good version )
Play has a fixed date, clic on the about button and it will shows:

    - In the playground the time begins at 2009-11-10 23:00:00 UTC
    (determining the significance of this date is an exercise for the reader).
    This makes it easier to cache programs by giving them deterministic output.

Il giorno mercoledì 3 dicembre 2014 13:30:32 UTC+1, Oleksandr Lobunets ha
scritto:
First of all, Playground use a fake time:
http://blog.golang.org/playground#TOC_3.1

Finally, the format string in the second example is wrong, since it does
not represent the reference time.


Regards Manlio

Il giorno mercoledì 3 dicembre 2014 13:49:43 UTC+1, Manlio Perillo ha
scritto:
The wrong one is the first example, not the second; sorry.


Regards Manlio

This helps me. I was initially very confused about this "reference time"
because it doesn't seem to be in the documentation, but the code makes it
very clear what it is.

https://golang.org/src/pkg/time/format.go#L61

It's in the doc with a nice example. Did you search at the wrong place?
( It's there : http://golang.org/pkg/time/#Time.Format )

Le mercredi 3 décembre 2014 15:59:46 UTC+1, Matthew Zimmerman a écrit :

No, I don't. I see the reference time for one specific case but it's not
spelled out clearly what each of those times represent.

Looking only at the documentation, how would you know that "January" is
what you put in your format if you want the month fully spelled out? What
if I want a two-digit year? Where is that in the documentation?

This isn't to point out that the documentation is lacking; I don't think it
needs it since the source is so clear. A reference to the source would be
nice I guess; just pointing out that I can agree with the original poster.
The source is so nice since it's exhaustive where the documentation only
provides an example.

I think you are looking for: http://golang.org/pkg/time/#pkg-constants

The point still stands that those predefined formats do not describe the
expected values of the layout in a complete way and if your time format is
not described there, it isn't clear how to make a custom layout that works.
The comments in time/format.go are good, but that documentation isn't
exported to godoc.

This is a common source of confusion because many people have experience
of other systems that use printf style tokens. I think the key phrase in
the docs that makes the Go way clear is this one:

"To define your own format, write down what the reference time would
look like formatted your way"

(from http://golang.org/pkg/time/#pkg-constants)

That's basically all you have to do.

Ian

But there are unstated non-obvious constraints, eg on month
names. Suppose my format is

     Mon Janvier 2 15:04:05 -0700 MST 2006

If I then display a time in the next month, will it use Février?

Chris

Yeah, I was quite disappointed when I wasn't able to
time.Now().Format("Stardate: -316994.7410895484")

Firstly the time on the playground is fixed to a specific time. That
explains the second one which is correct otherwise.

As for the first one - you need to use the magic date to specify the
format and 2006 is the year you need not 2014.

http://golang.org/pkg/time/#Parse

I think it is valid criticism that the docs on how to format times could be
much more complete as to what is actually supported. Writing it "your way"
will not work unless the code understands and expects "your way". What it
understands and expects should be better documented. You shouldn't ever
need to look at the source to see what is supported. One good example is
time zones.... from the predefined constants, I can see that "-0700" and
"MST" is supported, but is "Mountain Standard Time"? There's no way to
know except to read the source.