Edit in JSFiddle

$(".events, .close").click(function() {
    $(document.body).toggleClass("calendar");
});

FastClick.attach(document.body);
$(".event-item").click(function(){
    $(this).toggleClass("expanded");
});
<meta name="viewport" content="width=device-width, user-scalable=false;">
<div class="grid clearfix">
		<div class="day header"><span>S</span></div>
		<div class="day header"><span>M</span></div>
		<div class="day header"><span>T</span></div>
		<div class="day header"><span>W</span></div>
		<div class="day header"><span>T</span></div>
		<div class="day header"><span>F</span></div>
		<div class="day header"><span>S</span></div>
		<div class="day"><span>1</span></div>
		<div class="day"><span>2</span></div>
		<div class="day"><span>3</span></div>
		<div class="day"><span>4</span></div>
		<div class="day events">
            <span>5</span>
            <div class="event-number">99 events</div>
			<div class="event-bullet">&bull;</div>
        </div>
		<div class="day"><span>6</span></div>
		<div class="day"><span>7</span></div>
		<div class="day events">
            <span>8</span>
                        <div class="event-number">1 event</div>
			<div class="event-bullet">&bull;</div>

    </div>
		<div class="day">
            <span>9</span>
        </div>
		<div class="day"><span>10</span></div>
		<div class="day"><span>11</span></div>
		<div class="day"><span>12</span></div>
		<div class="day"><span>13</span></div>
		<div class="day"><span>14</span></div>
		<div class="day"><span>15</span></div>
		<div class="day events">
            <span>16</span>
                        <div class="event-number">3 events</div>
			<div class="event-bullet">&bull;</div>

    </div>
		<div class="day">
            <span>17</span>
        </div>
		<div class="day"><span>18</span></div>
		<div class="day"><span>19</span></div>
		<div class="day"><span>20</span></div>
		<div class="day"><span>21</span></div>
		<div class="day"><span>22</span></div>
		<div class="day">
            <span>23</span>
        </div>
		<div class="day events">
            <span>24</span>
                        <div class="event-number">88 events</div>
			<div class="event-bullet">&bull;</div>

    </div>
		<div class="day"><span>25</span></div>
		<div class="day"><span>26</span></div>
		<div class="day events">
            <span>27</span>
            <div class="event-number">14 events</div>
			<div class="event-bullet">&bull;</div>
        </div>
		<div class="day"><span>28</span></div>
		<div class="day"><span>29</span></div>
		<div class="day"><span>30</span></div>
		<div class="day"></div>
		<div class="day"></div>
		<div class="day"></div>
		<div class="day"></div>
		<div class="day"></div>
</div>


<div class="event-container">
<header>
    <span class="close">&times;</span>
    <h1>Monday September 16</h1>
    <p class="instructions">Click on an event to see more info.</p>
</header>
<ul>
    <li class="event-item clearfix">
        <div class="image">
            <img src="http://placekitten.com/100/100">
        </div>
        <div class="event-body">
        <h3 class="event-title">Event 1</h3>
        <span class="event-time">11 am</span>
            <span class="expand">&times;</span>
        <section class="teaser">
            <p> A short description.  Maybe like two or three sentences.  Just a teaser of what's inside.  </p>
        </section>
        <section class="full-info">
            <summary class="description">
                <p> A longer description of the event.  We can go wild here, a paragraph or two even.  Lot's of information about the event can go here.  </p>
                <p> You should come to this event because it's going to be fun.  So much fun.  </p>
            </summary>
            <div class="location">
                <strong>Liberty Science Center</strong>,
                <div>222 Jersey City Blvd.</div>
                <div>Jersey City</div>
                <div>Visit <a href="#">http://example.com/</a> for more info</div>
            </div>
        </section>
        </div>
    </li>
    <li class="event-item clearfix">
        <div class="event-body">
        <h3 class="event-title">Event 2</h3>
        <span class="event-time">All Day</span>
        <span class="expand">&times;</span>
        <section class="teaser">
            <p> A second event description.  Also two or three sentences.  Just a teaser of what's inside.  </p>
        </section>
        <section class="full-info">
            <summary class="description">
                <p> A longer description of the event.  We can go wild here, a paragraph or two even.  Lot's of information about the event can go here.  </p>
                <p> You should come to this event because it's going to be fun.  So much fun.  </p>
            </summary>
            <div class="location">
                <strong>Cricket Hill Brewery Co.</strong>,
                <div>24 Kulick Rd.</div>
                <div>Fairfield</div>
                <span>Call 973-276-9415 or visit <a href="#"> www.CricketHillBrewery.com</a></span>
            </div>
        </section>
        </div>
    </li>
    <li class="event-item clearfix">
        <div class="image">
            <img src="http://placekitten.com/g/64/64">
        </div>
        <div class="event-body">
        <h3 class="event-title">Event 1</h3>
        <span class="event-time">11 am</span>
        <span class="expand">&times;</span>
        <section class="teaser">
            <p> A short description.  Maybe like two or three sentences.  Just a teaser of what's inside.  </p>
        </section>
        <section class="full-info">
            <summary class="description">
                <p> A longer description of the event.  We can go wild here, a paragraph or two even.  Lot's of information about the event can go here.  </p>
                <p> You should come to this event because it's going to be fun.  So much fun.  </p>
            </summary>
            <div class="location">
                <strong>Liberty Science Center</strong>,
                <div>222 Jersey City Blvd.</div>
                <div>Jersey City</div>
                <div>Visit <a href="#">http://example.com/</a> for more info</div>
            </div>
        </section>
        </div>
    </li>
    <li class="event-item clearfix">
        <div class="event-body">
        <h3 class="event-title">Event 2</h3>
        <span class="event-time">All Day</span>
        <span class="expand">&times;</span>
        <section class="teaser">
            <p> A second event description.  Also two or three sentences.  Just a teaser of what's inside.  </p>
        </section>
        <section class="full-info">
            <summary class="description">
                <p> A longer description of the event.  We can go wild here, a paragraph or two even.  Lot's of information about the event can go here.  </p>
                <p> You should come to this event because it's going to be fun.  So much fun.  </p>
            </summary>
            <div class="location">
                <strong>Cricket Hill Brewery Co.</strong>,
                <div>24 Kulick Rd.</div>
                <div>Fairfield</div>
                <span>Call 973-276-9415 or visit <a href="#"> www.CricketHillBrewery.com</a></span>
            </div>
        </section>
        </div>
    </li>
    <li class="event-item clearfix">
        <div class="image">
            <img src="http://placekitten.com/64/64">
        </div>
        <div class="event-body">
        <h3 class="event-title">Event 1</h3>
        <span class="event-time">11 am</span>
        <span class="expand">&times;</span>
        <section class="teaser">
            <p> A short description.  Maybe like two or three sentences.  Just a teaser of what's inside.  </p>
        </section>
        <section class="full-info">
            <summary class="description">
                <p> A longer description of the event.  We can go wild here, a paragraph or two even.  Lot's of information about the event can go here.  </p>
                <p> You should come to this event because it's going to be fun.  So much fun.</p>
            </summary>
            <div class="location">
                <strong>Liberty Science Center</strong>,
                <div>222 Jersey City Blvd.</div>
                <div>Jersey City</div>
                <div>Visit <a href="#">http://example.com/</a> for more info</div>
            </div>
        </section>
        </div>
    </li>
</ul>
</div>


    <script type="text/template" id="event-template">
            <li class="event-item clearfix">
        <div class="image">
            <img src="http://placekitten.com/100/100">
        </div>
        <div class="event-body">
        <h3 class="event-title"><%= event.title %></h3>
        <span class="event-time">11 am</span>
        <section class="teaser">
            <p><%= event.teaser %></p>
        </section>
        <section class="full-info">
            <summary class="description">
				<%= event.description %>
            </summary>
            <div class="location">
                <strong><%= event.location.title %></strong>,
                <div><%= event.location.street_number %> <%= event.location.street_name %></div>
                <div><%= event.location.city %></div>
            </div>
        </section>
        </div>
    </li>
 </script>



* {
    //margin: 0;
    box-sizing: border-box;
}
body.calendar {
    .grid {
        display: block;
    }
    .event-container {
        display: none;
    }
}
body:not(.calendar) {
    .grid {
        display: none;
    }
    .event-container {
        display: block;
    }
}
body {
    font-family: "Helvetica Neue";
    font-weight: 200;
    background-color: #ddd;
}
.grid {
    padding: 0.5em;
    max-width: 968px;
    min-width: 300px;
    //position: relative;
    margin: 0 auto;
    background-color: white;
}
$width = 2px;
.grid .header {
    //width: 100%;
    font-weight: 400;
    margin-bottom: 4px;
    background-color: #333;
    color: #ddd;
    //outline: 2px solid white;

}
.grid .day:nth-child(7n) {
    margin-right: 0;
}
$day-color = #ebebeb
.day {
    background-color: $day-color;
    //background-color: #e6e6e6;
    //display: inline-block;
    float: left;
    width: 18px;
    width: 13.8571%;
    //width: calc('14.2857% - #{$width}');
    //width: calc('(100% - #{6 * $width}) / 7');
    padding: 1.8em 0 2em;
    margin: 0 0.5% 0.5% 0;
    //margin-bottom: 0.5%;
    text-align: center;
    //border-bottom: 2px solid white;
    position: relative;
    //margin-right: $width;
    //margin-right: 0.5%;
}
.events {
    background-color: darken($day-color, 4%);
    //padding: 1.25em 0;
    //color: #278ed3;
    font-weight: 400;
}
.event-number {
    position: absolute;
    left: 0;
    right: 0;
    line-height: 0.5;
}
.event-bullet {
    display: none;
    position: absolute;
    left: 0;
    right: 0;
    line-height: 0.5;
}
.day.events div {
    //text-decoration: underline;
}

.grid .day:empty {
    border: none;
    background-color: rgba(0,0,0,0);
    //outline: none;
}

.clearfix{
    *zoom:1;
}
.clearfix:before,.clearfix:after{
    display:table;
    content:" ";
    //line-height:0;
}
.clearfix:after{
    clear:both;
}

@media all and (max-width: 600px) {
    .events .event-number {
        display: none;
    }
    .events .event-bullet {
        display: block;
    }
    .days {
        padding: 1.8em 0;
    }
    body {
        //background-color: purple;
    }
}

@media all and (max-width: 480px) and (min-width: 320px) {
    body {
        //background-color: red;
    }
    .day.events, .day {
        padding: 1.2em 0;
    }
}

@media all and (max-width: 320px) {
    body {
        //background-color: blue;
    }
    .day.events {
        //padding: 0.75em 0;
    }
    .event-bullet {
        line-height: 0.5;
    }
    .grid .day {
        padding: 1em 0;
    }
}


body {
    font-family: "Helvetica Neue", Helvetica, sans-serif;
    overflow: scroll;
    background-color: #ddd;
    color: #333;
}

.event-container {
    width: 75%;
    max-width: 968px;
    min-width: 300px;
    margin: 0 auto;
.event-title {
    display: inline-block;
    line-height: 1;
    margin: 0em;
}
    .close {
        /*position: absolute;
        right: 5%;
        top: 5%;*/
        float: right;
    }
header {
    position: relative;
    h1 {
        font-size: 1.9em;
        margin-bottom: 0.1em;
    }
    p {
        margin: 0;
        font-size: 0.9em;
    }
}

ul {
    list-style: none;
    padding-left: 0;
}

.event-item {
    overflow: hidden;
    border-radius: 2px;
    clear: both;
    background-color: white;
    box-shadow: 3px 3px black;
    border: 1px solid black;
    padding: 0.5em;
    margin: 1em 0;
    .expand {
        -webkit-transform: rotate(45deg);
        -webkit-transition: -webkit-transform 0.5s;
        position: absolute;
        right: 0;
        line-height: 0.7;
        vertical-align: middle;
    }
    .image {
        float: left;
        margin-right: 1em;
        img {
            display: block;
        }
    }
    .event-body {
        overflow: hidden;
        //min-height: 64px;
        position: relative;
    }
    .location {
        margin-top: 1em;
    }
    p {
        margin-bottom: 0;
    }
    /*.description {
        -webkit-transition-property: height;
        -webkit-transition-duration: 2s;
        -webkit-transition-timing-function: ease;
        //transition: opacity 0.5s ease, height 1s;
    }*/
    &.expanded {
        .teaser {
            display: none;
            /*
            visibility: hidden;
            height: 0;
            margin: 0;
            */
        }
        .full-info {
            display: block;
            //opacity: 1;
        }
        .expand {
            -webkit-transform: rotate(0);
        }
    }
    &:not(.expanded) .full-info {
        display: none;
        /*height: 0;
        visibility: hidden;
        opacity: 0;*/
    }
}
@media all and (max-width: 470px) {
    header h1 {
        font-size: 1.7em;
    }
}

}