f0rest8

f0rest8

Format a DateTime using :strftime with the offset calculated in the hours

I know I’m missing something here, but I’ve bounced around from Calendar and Timex trying to get a :strftime format with the offset computed in the formatted hours to no avail.

Is there a way to format a DateTime string using :strftime but computing the offset in the hours representation?

Currently, I convert a NaiveDateTime with Timex so that I can see what Calendar's calculating as the offset (which shows that everything is correct time-wise — just not my formatting ability).

dt = Timex.to_datetime(naive_date_string, "America/New_York")
datetime = Calendar.strftime(dt, "%A %b. %d, %Y @ %I:%M %z")

"Friday Aug. 20, 2021 @ 06:14 -0400"

It seems like whenever I come back to formatting using :strftime I arrive back in the future because the offset is not able to be computed in the formatted hours.

When I use the %z to see what the offset is, it’s correct and leaves me wishing I could just use something like %I only with the offset computed from the inputted datetime.

:blush:

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vfsoraki

vfsoraki

So you’re basically trying to convert your datetimes to UTC?

I think shift_zone/3 might be useful to you, or if you use Timex I think convert/2 might be useful.

I think you want to convert your datetimes to “Etc/UTC” or similar.

acrolink

acrolink

For anyone looking for the straightforward answer to this very basic need (not documented anywhere), can be done like this:

DateTime.shift_zone!(DateTime.from_naive!(record.inserted_at, "UTC"), "Asia/Jerusalem")
vfsoraki

vfsoraki

+hhmm/-hhmm time zone offset from UTC (empty string if naive)

%z already gives you the offset in hours and minutes.

I’m not sure I understood your problem, care to clarify more? What do you mean by “hours representation”?

vfsoraki

vfsoraki

Also, if you just need the offset, you can use DateTime struct directly, using fields utc_offset and std_offset which are in seconds, but you can convert them to hours if you wish.

vfsoraki

vfsoraki

You’re welcome.

BTW, I think I pasted the second link wrong, here it is: Timex.Timezone — timex v3.7.6

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