Two css class border on the one part left - html

Question

I have to class
<div class="thread-entryresponse">
<div class="date">
</div>
</div>
then
<div class="thread-entrymessage">
<div class="date">
</div>
</div>
my css code is
.thread-entryresponse {
border-left: 2px solid #428bca;
color: #444;
padding: 10px;
}
.thread-entrymessage {
border-right: 2px solid #444;
}
.date {
color: #444;
margin-top: 20px;
padding: 10px;
}
I am trying to do below
if .thread-entryresponse and .date then border-left: 2px solid #428bca; on the date
if .thread-entrymessage and .date then border-right: 2px solid #444;
on the date
note that the date is inside of the thread-entryresponse and thread-entrymessage

Answer 1

First, I strongly recommend you learn basics in HTML/CSS
Second, you can use this
DEMO
.thread-entryresponse .date {
border-left: 2px solid #428bca;
}
.thread-entrymessage .date {
border-right: 2px solid #444;
}

Answer 2

As you say:
.date is inside of the .thread-entryresponse and .thread-entrymessage
This means that .date is a descendant of .thread-entryresponse and .thread-entrymessage. To vary the style of .date according to its parent, use the descendant selector:
Markup:
<div class="thread-entryresponse">
<div class="date"></div>
</div>
<div class="thread-entrymessage">
<div class="date"></div>
</div>
CSS:
.thread-entryresponse .date {
border-left: 2px solid #428bca;
}
.thread-entrymessage .date{
border-right: 2px solid #444;
}
Demo