Super Spread Sheet S³

Or little computing tricks and hacks

Dear App, why are you giving me the wrong date?

Localization has always amazed me. But I also giggle when developers get it wrong. I know for experience that it is not obvious. How does the app know what language do you speak if you leave in Montreal, Switzerland or Belgium, where there are more than one official language? And that is when when the user wants to use the app in one of the official languages.

Added to that are the timezones and daylight savings shifts in one place throughout the year. I am originally from Colombia, where even the notion of seasons is summarized as the rain and dry seasons. Don’t ask me when each is supposed to be! Change of time in Summer? Forget it. “Wow, are you really going to sleep now, aunty, here we are going to have lunch!” The internet brings these issues to the fore and forces the need for solutions. The infrastructure is there to be used.

The last time I stumbled upon timezones was when implementing the events section of my Rails app. The first surprise was to find that the time I saved was shifted. The reason made perfect sense. The canonical storage timezone in the database is UTC and the display can be done in a timezone of your choice. Cool. I adjusted the configuration and added to the config/application.rb file the following line:

    config.time_zone = 'Eastern Time (US & Canada)'

That worked just fine in my local development platform: the storage was done in UTC and the display in EST/EDT depending on the time of the year, with the following code:

    event.my_date.to_formatted_s(:long_ordinal)
    event.my_date.zone %>

But when I deployed to heroku, the initial problem came back. I realized that it had something to do with the local timezone of the machine, somehow. As would only make sense, the heroku server is running in UTC time. However, even if the default timezone read EST, the actual saving into the database was done simply by striping the timezone: 17h00 EST became 17h00 UTC.

I could not find a reason, but that does not matter. The point is to make the app work standalone, independently of where it is deployed.

I tried several paths:

1. I added an extra line to the config/application.rb as follows:

    config.active_record.default_timezone = 'Eastern Time (US & Canada)'

However, that line just made the previously saved my_date fields disappear.

2. I then used the use_zone command to create a block, where the default timezone would be defined:

Time.use_zone("Eastern Time (US \& Canada)") {
        time_entered = Time.new(
          params[:date]['year'].to_i,
          params[:date]['month'].to_i,
          params[:date]['day'].to_i,
          params[:date]['hour'].to_i,
          params[:date]['minute'].to_i,
        )
        @event.the_date = time_entered
      }

This was a step forward, the time_entered was produced in the correct timezone but the assignment and then saving in the database, simply stripped off the timezone information.

3. After much trial and error, the solution was to create an object with the UTC offset. This offset had to be dependent on the entered date, as daylight savings for that date is what matters.

The final solution is:

      Time.use_zone("Eastern Time (US \& Canada)") {
        time_entered = Time.new(
          params[:date]['year'].to_i,
          params[:date]['month'].to_i,
          params[:date]['day'].to_i,
          params[:date]['hour'].to_i,
          params[:date]['minute'].to_i,
        )
        the_offset = Time.zone.parse(time_entered.to_s).utc_offset
        new_time = Time.new(
          params[:date]['year'].to_i, 
          params[:date]['month'].to_i,
          params[:date]['day'].to_i,
          params[:date]['hour'].to_i,
          params[:date]['minute'].to_i,
          0,
          the_offset
        )
        @event.my_date = new_time
      }

The code for viewing the date, did not change.

If you have any further comments or explanations, please send them this way.

Sources

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