SysTime.toISOExtString with timezone offset

[Jonathan M Davis via Digitalmars-d-learn]

On Monday, April 20, 2015 08:10:40 Jack Applegame via Digitalmars-d-learn wrote:
> I need current system time ISO string with timezone offset. For
> example
> "2015-04-20T11:00:44.735441+03:00"
> but Clock.currTime.toISOExtString doesn't write offset:
> "2015-04-20T11:00:44.735441+03:00"
>
> I found workaround, but it looks redundant and needs memory
> allocation:
>
> auto t = Clock.currTime;
> t.timezone = new immutable SimpleTimeZone(t.utcOffset);
> writeln(t.toISOExtString);
>
> Is there a simple way to get time ISO string with timezone offset?

The ISO standard requires that a lack of time zone in the string be treated
as local time, so SysTime, does not print the timezone offset as part of the
string for LocalTime (though the standard requires that the lack of timezone
be treated as local time, not that local time always be printed with no time
zone, so I suppose that the current behavior is not strictly-speaking
necessary). That being the case, you will have to use a different TimeZone
than LocalTime if you want an offset.

Doing toUTC().toISOExtString() will convert it to UTC, and you'll end up
with z for the offset, but obviously, the time will not be the same, since
it'll be adjusted to UTC. However, that's what I'd suggest that folks do in
most cases. And that won't allocate, since UTC is a singelton.

The only other alternative at present (other than adding the offset to the
string yourself) is to do like you're doing and allocate a SimpleTimeZone
(or if you know what your time zone is, use PosixTimeZone or
WindowsTimeZone).

Perhaps, LocalTime should be changed so that it prints the time zone out
(and just make it so that the lack of time zone is read in as local time
rather than treating it that way in both directions), but that's not how it
works currently.

- Jonathan M Davis