Change date and time to Japanese notation in Rails


You can use the table column created_at to retrieve the date and time when the data was created. However, it is difficult to use it as it is.

This time, I would like to be able to retrieve it with a notation such as 2020/7/21 9:05:50.

Display the creation date and time

First, let's extract the created_at of the data @ post in the posts table as it is.


<p>Event: <%= @post.event %></p>
<p>place: <%= %></p>
<p>Creation date and time: <%= @post.created_at %></p>
place event created_at
Tokyo Fireworks display 2020-07-21 00:05:50 UTC

You can see that it is very different from the target 2020/7/21 9:05:50 notation.

Specifically, the following three points are different.

  1. ʻUTC` (World Standard Time)
  2. / is replaced with -
  3. The notation of 7 is 07

I would like to correct it in order.

1. Change from World Standard Time to Japan Time

Since programming is used all over the world, it will be output in World Standard Time as it is. Therefore, let's change it to Japan time.


class Application < Rails::Application
  # *****Add the following line*****
  config.time_zone = "Asia/Tokyo"

By inserting this one line, I was able to change World Standard Time to Japan Time as shown below.

place event created_at
Tokyo Fireworks display 2020-07-21 09:05:50 +0900

There is a +0900, which means that the time difference between Japan time and World Standard Time is +9 hours.

2. Change the format

It's Japan time, but it's hard to understand if the format is 2020-07-21 09:05:50 + 0900. Let's change it.

First, install the gem for multilingual support and set it to Japanese.


#For Rails6
gem 'rails-i18n', '~> 6.0'
#For Rails5
gem 'rails-i18n', '~> 5.1'


bundle install


class Application < Rails::Application
  config.time_zone = "Asia/Tokyo"
  # *****Add the following line*****
  config.i18n.default_locale = :ja

Then use the l method provided by rails-i18n.


<p>Event: <%= @post.event %></p>
<p>place: <%= %></p>
<!-- *****add l***** -->
<p>Creation date and time: <%= l @post.created_at %></p>

In addition, let's create a file called config / locales / ja.yml and set the format.


      default: "%Y/%m/%d %H:%M:%S"

As a result, the notation changes as follows, and +0900 also disappears.

place event created_at
Tokyo Fireworks display 2020/07/21 09:05:50

The format can be changed freely, for example, if you don't need seconds, you can omit:% S.


      default: "%Y/%m/%d %H:%M"
place event created_at
Tokyo Fireworks display 2020/07/21 09:05
Symbol Meaning
% Y Year
% m Month (MONTH)
% d DAY
% M Minutes (MINUTE)
% S seconds (SECOND)

[Reference page] Ruby 2.7.0 Reference Manual (strftime)

3. Eliminate zero (0) padding

For example, it is unnatural for July to be written as 07, so let's remove 0.


      # ***** %Behind-Add*****
      default: "%Y/%-m/%-d %-H:%M:%S"
place event created_at
Tokyo Fireworks display 2020/7/21 9:05:50

By inserting -, we were able to eliminate 0 padding as described above.

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