How to Use :date_started to Figure Out :levels? - ruby-on-rails

Question

When a User starts a habit he chooses his date_started in the form.
How can we use date_started as the start point to figure out and display in the index what level the User is on?
A certain amount of days must pass before the User moves onto the next level (as shown below in the model).
Currently when a User looks at the index all his habits will show "Mastered" regardless of what the date_started is. Thanks in advance for your expertise =]
form
<label> Started: </label>
<%= f.date_select :date_started, :order => [:month, :day, :year], class: 'date-select' %>
class Habit < ActiveRecord::Base
belongs_to :user
validates :action, presence: true
serialize :committed, Array
scope :missed, -> { where(missed: 1) }
scope :nonmissed, -> { where(missed: 0) }
def levels
case committed
when 0..9
1
when 10..24
2
when 25..44
3
when 45..69
4
when 70..99
5
else
"Mastered"
end
end
end
controller
class HabitsController < ApplicationController
before_action :set_habit, only: [:show, :edit, :update, :destroy]
before_action :correct_user, only: [:edit, :update, :destroy]
before_action :authenticate_user!, except: [:index, :show]
def index
#habits = Habit.all.order("date_started DESC")
#missed_habits = current_user.habits.missed
#nonmissed_habits = current_user.habits.nonmissed
end
def show
end
def new
#habit = current_user.habits.build
end
def edit
end
def create
#habit = current_user.habits.build(habit_params)
if #habit.save
redirect_to #habit, notice: 'Habit was successfully created.'
else
render action: 'new'
end
end
def update
if #habit.update(habit_params)
redirect_to #habit, notice: 'Habit was successfully updated.'
else
render action: 'edit'
end
end
def destroy
#habit.destroy
redirect_to habits_url
end
private
def set_habit
#habit = Habit.find(params[:id])
end
def correct_user
#habit = current_user.habits.find_by(id: params[:id])
redirect_to habits_path, notice: "Not authorized to edit this habit" if #habit.nil?
end
def habit_params
params.require(:habit).permit(:missed, :left, :levels, :date_started, :trigger, :action, :target, :positive, :negative, :committed => [])
end
end

Answer 1

Try something like this:
def levels
n_days = Integer(Date.today - date_started)
case n_days
when 0..9
1
when 10..24
2
...
end