Strange syntax error when using ruby injection in html

The error I am getting is:

SyntaxError in PagesController#main

C:/Users/Sarah/RubymineProjects/MyApp/app/views/calendars/_show.html.erb:49: syntax error, unexpected ')', expecting keyword_then or ';' or '\n' ...=( if event.starts_at.monday? );@output_buffer.safe_append=' ... ^ C:/Users/Sarah/RubymineProjects/MyApp/app/views/calendars/_show.html.erb:52: syntax error, unexpected keyword_end, expecting ')' '.freeze; end ^ C:/Users/Sarah/RubymineProjects/MyApp/app/views/calendars/_show.html.erb:54: syntax error, unexpected keyword_end, expecting ')' '.freeze; end ^ C:/Users/Sarah/RubymineProjects/MyApp/app/views/calendars/_show.html.erb:364: syntax error, unexpected keyword_ensure, expecting ')' C:/Users/Sarah/RubymineProjects/MyApp/app/views/calendars/_show.html.erb:366: syntax error, unexpected keyword_end, expecting ')'

but the code I'm trying to write is:

<% @events.each do |event|%>
        <%= if event.starts_at.monday? %>

            <p><%= event.name %></p>
            <% end %>

        <% end %>

Is this really because of my syntax (which I think seems fine) or is it a problem with my code somewhere? I am writing this code in _show.html.erb (from calendars controller) which is a partial that is being rendered in my main.html.erb (from Pages controller)

this is the code I'm using to render my partial:

<%= render partial: '/calendars/show', locals: {} %>

and here are my controllers and models:

class PagesController < ApplicationController

  #before_action :require_customer, only: [:main]

  def home

  end


  def main
    @events = current_customer.calendar.events
  end

end

my calendar controller:

class CalendarsController < ApplicationController

  def new
    @calendar = Calendar.new(calendar_params)

  end

  def create
    @calendar = Calendar.new(calendar_params)
  end

private
  def calendar_params
    params.require(:customer_id)
  end


  def show
    @calendar = current_customer.calendar
    @events = @calendar.events

  end

end

my events controller (just for reference)

class EventsController < ApplicationController
  before_filter :logged_in?


  def new
    @event = Event.new
    @calendar = current_customer.calendar

  end


  def create

    @calendar = current_customer.calendar

    @event = @calendar.events.build(event_params)

    if @event.save
      redirect_to '/main' #'/main/#{@calendar.id}'
    else
      redirect_to '/compose'
      end

  end

private
  def event_params
    params.require(:event).permit(:calendar_id, :name, :starts_at, :ends_at) 
  end

also here are my calendar and events models:

class Calendar < ActiveRecord::Base
  belongs_to :customer
  has_many :events
end


class Event < ActiveRecord::Base
  belongs_to :calendar

  end

I've been stuck on this for days I just can't seem to find an explanation. Thanks!