All the date/time formatting options are managed within the library at jl_last_updated/libraries/jl/time_presentation.php
That is the file to edit if you want to add further date/time formatting options.
In the block view and template CSS classes are attached to everything and spans added with classes for convenient theming.
With concrete5.6+ this addon also exports its core functionality as symbols to Magic Data:
LAST_UPDATED - The time a page was last updated.
FRIENDLY_DATE - Formats a date or time in human-friendly way