Format time_select to nearest 15th minute

time_select is a nice little rails helper that generates dropdown lists for populating time fields, like this:

However, it can get a bit messy for users when they come to use the thing, displaying every minute from 1-60 like this:

You can dress it up nice though by using the :minute_step option. Setting it to 15 just lists the options 0, 15, 30 and 45 like this:

<%= time_select :gig, :doors_open, :minute_step> 15 %>