Timex.now(timezone)

Maybe the production deployment server doesn’t have daylight savings enabled?

Do you have access to it? Can you test with the usual UNIX commands on the terminal?

I can test that for sure, but this happens locally too. If I send the report in a development environment it will be an hour behind.

If I understand correctly, you have a different result for that instruction in your app and in your local terminal?

My approach would be to identify what is different.
I can see potentially two things when calling Timex.now/1 (never used the lib but had a quick look at its code).

1. It calls :os.system_time()
2. It relies on tzdata lib.

Would you be able to, once from the app and once from your local terminal, check the output of :os.system_time() and Tzdata.version() ?

Then maybe your local and production DBs don’t have the daylight savings activated? Just shooting in the dark, it’s the first good assumption I could make.

I think I’ve realized the issue. Our code was actually using Timex.now("MST") I thought MST and MDT were interchangeable or that Timex would account for daylight saving time. It seems like MST will be incorrect about 8 months out of the year, I can’t verify MDT seems like America/Denver is the way to go.

@dimitarvp your daylight savings mention got me on this track.

“MST” used as a time zone ID has a constant offset of -7 hours from UTC for the whole year. It’s not a bug. It’s a rule written in the IANA time zone database.

“America/Denver” is a time zone ID and MST/MDT are abbreviations for that time zone.

I didn’t say it’s a bug, when I said “incorrect” I just meant in the case where we had used it to display text on an email. You mention the offset for MST, is MDT then going to be -6 hours from UTC for the whole year as well?

I think I confuse you more:) but the IANA tz database can be very confusing.

“MST” can be used as a time zone ID; but for example “MDT” seems not to be a valid time zone ID.

^ So this should actually throw an error

Anyway, this is not what you want. You want to use “America/Denver” as a time zone ID.

When you use “America/Denver” as a time zone ID, the offset will change throughout the year:
-07:00/MST and -06:00/MDT

It doesn’t throw an error, it just gives the current time (since we are in daylight time). But I am now using “America/Denver” as the time zone ID for much of the app. Thanks @thojanssens1.

This is actually how timezones work. Timezone names alike MDT are names for certain UTC offsets. Area names like “America/Denver” are the names, which define which of those timezones is in effect in a certain area of the world at a certain time.