Improve translation documentation

docs/translations.markdown

@@ -32,12 +32,29 @@ How to add new translated text in the application?
 
 Translations are displayed with the following functions in the source code:
 
-- `t()`: escaped HTML text
-- `e()`: displayed with no escaping
-- `dt()`: date using `strftime()` formats
+- `t()`: dispaly text with HTML escaping
+- `e()`: display text without HTML escaping
+- `dt()`: display date and time using the `strftime()` function formats
 
 Always use the english version in the source code.
 
+### Date and time translation
+
+Date strings use the function `strftime()` to format the date.
+
+By example, the original English version can be defined like that `Created on %B %e, %Y at %k:%M %p` and that will output something like that `Created on January 11, 2015 at 15:19 PM`. The French version can be modified to display a different format, `Créé le %d/%m/%Y à %H:%M` and the result will be `Créé le 11/01/2015 à 15:19`.
+
+All formats are available in the [PHP documentation](http://php.net/strftime).
+
+### Placeholders
+
+Text strings use the function `sprintf()` to replace elements:
+
+- `%s` is used to replace a string
+- `%d` is used to replace an integer
+
+All formats are available in the [PHP documentation](http://php.net/sprintf).
+
 How to find missing translations in the applications?
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