In 2025 this still works in Rails, but it is likely better to rely on other methods like defining time formats in the Rails I18n system yaml files and using I18n.l rather than Time.to_fs(:format)

If you need to set up custom date formats in Rails, for example to show in Views, you can do so by creating a config/initializers/time_formats.rb file and adding as many of the following as you want:

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Time::DATE_FORMATS[:au_datetime] = '%e/%m/%Y %I:%M%P'
Time::DATE_FORMATS[:au_date] = '%e/%m/%Y'

You can even use lambdas when defining a format, which will be executed using .call when you call to_s on your Time:

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Time::DATE_FORMATS[:short_ordinal]  = ->(time) { time.strftime("%B #{time.day.ordinalize}") }

This is covered in more detail in the Rails Time documentation here:

https://api.rubyonrails.org/classes/Time.html#method-i-to_fs