racheev,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
.red{
border: solid 1px #FF0000;
border-radius: 2px;
}
</style>
</head>
<body>
<div id="calendar" align="center">
<table class="tablecall">
<tr>
<td>
<a class="arrow" id="prev" onclick="cal(prev);"> <<< </a>
</td>
<td>
<table class="tablecall">
<tr class="trcall">
<td colspan="7">Выбираем <span id="date"></span></td>
</tr>
<tr class="trcall">
<td>Пн</td>
<td>Вт</td>
<td>Ср</td>
<td>Чт</td>
<td>Пт</td>
<td><font color="red">Сб</font></td>
<td><font color="red">Вс</font></td>
</tr>
<tr class="day">
<td id="col1"></td>
<td id="col2"></td>
<td id="col3"></td>
<td id="col4"></td>
<td id="col5"></td>
<td id="col6"></td>
<td id="col7"></td>
</tr>
<tr class="day">
<td id="col8"></td>
<td id="col9"></td>
<td id="col10"></td>
<td id="col11"></td>
<td id="col12"></td>
<td id="col13"></td>
<td id="col14"></td>
</tr>
<tr class="day">
<td id="col15"></td>
<td id="col16"></td>
<td id="col17"></td>
<td id="col18"></td>
<td id="col19"></td>
<td id="col20"></td>
<td id="col21"></td>
</tr>
<tr class="day" id="week4">
<td id="col22"></td>
<td id="col23"></td>
<td id="col24"></td>
<td id="col25"></td>
<td id="col26"></td>
<td id="col27"></td>
<td id="col28"></td>
</tr>
<tr class="day" id="week5">
<td id="col29"></td>
<td id="col30"></td>
<td id="col31"></td>
<td id="col32"></td>
<td id="col33"></td>
<td id="col34"></td>
<td id="col35"></td>
</tr>
<tr class="day" id="week6">
<td id="col36"></td>
<td id="col37"></td>
<td id="col38"></td>
<td id="col39"></td>
<td id="col40"></td>
<td id="col41"></td>
<td id="col42"></td>
</tr>
</table>
</td>
<td><a class="arrow" onclick="cal(next);"> >>> </a></td>
</tr>
</table>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
var db = {"today":"09","year":"2018","month":"07","dayofmonth":"31","date":"2018-07","tomonth":"06","toyear":"2018","next":"2018-08","prev":"2018-06","day":"7","positions":[{"d":"10"},{"d":"11"}]};
var view = db['positions'];
var busy = view.map(function(e) {
return +e.d
});
var length = +db['dayofmonth'];
var today = +db['today'];
var day = +db['day'];
for (var i = 0; i < length; i++) {
var num = i + 1;
var html = num + '<br><input class="check" type="checkbox" name="day_view[]" value="" onclick="clk(this);">';
if (busy.indexOf(num) > -1 || num <= today ) html = num + '<br>-';
var id = "#col" + (i + day);
$(id).html(html).toggleClass("red", num == today)
}
</script>
</body>
</html>