Time periods in settings

[accessd]

This is a feature to specify time periods. Something like a number with select tag(days, weeks, months).

[accessd]

I tried to implement it in https://github.com/accessd/rails-settings-ui/tree/time-periods but is not yet clear how best to store time periods. If we'll store like string '7.days' then we need modify getting setting, that return seconds count.