Based on deleted https://github.com/gacha/gacha.id.lv/blob/master/_plugins/i18n_filter.rb

1. Add jekyll-i18n-date to _plugins folder of your site.
2. Create folder _locales and put some locale files from https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale there.
3. Add lang variables to _config.yaml or to frontmatter of any page/post like this:

lang: de

4. Localize your Date/DateTime/Time variables with

 {{ page.date | localize: "%d.%m.%Y" }}

or

 {{ post.date | localize: "%d.%m.%Y", "es" }}
 

1. Lang parameter in liquid
2. Page
3. Site

If no locale file for language parameter is found in _locales or date is nil, default date format is displayed. If "date" happens to be an integer value, it is converted with Time.at() (this rather suprising behaviour should probably be changed)