Re: How to make groff use local timezone?

[G. Branden Robinson]

Hi Jim!

At 2020-12-12T21:19:38-0800, Jim Avera wrote:
> The registers \n[mo] \n[dy] etc. seem to not respect the current time
> zone,

As far as I know, this is _not_ the case; groff sets its date/time
registers based upon the local time when the troff process starts.

You can inspect your local installation's behavior with a one-liner.

$ groff
.tm \n[year]-\n[mo]-\n[dy] \n[hours]:\n[minutes]:\n[seconds]
[Control+D]

For example, when I did this, I got "2020-12-14 10:33:16" (I'm in a
fairly "advanced" time zone).

> and so (for example) the \*(DT string provided by -mm shows the
> wrong day for several hours each day.

Now this part is interesting.  A similar one liner reveals a surprising
difference.

$ groff -mm
.tm \*[DT]

...I get "December 13, 2020".  I ran the above _after_ the previous
example, so something is definitely afoot here.

> I suspect groff is always in UTC (but haven't confirmed).  

No, that is not true, at least not in groff as provided by GNU.  A
downstream distributor, like a GNU/Linux distribution, could alter this.

> Is this a bug or intended?

There have been suggestions to _make_ UTC the default, or at least to
provide an option enabling it, to better facilitate reproducible build
efforts.

> How can I make mm's \*(DT show the correct date in my timezone? I know
> I can manually override the automatic value using .ND and some kind of
> wrapper script to auto-insert the macro call or something... but
> that's not very attractive.

It seems to me like mm's DT string is already doing this.  When I get a
chance I will examine the implemenation and follow up further.

Regards,
Branden

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