If date post is lower than...

Hi there,

I've got a question about categories.

I need to check in list of posts, if post is added (published) not later than eg. 3 hours.

For example:

if post publish date < 3 hours {

echo 'This post is new!';
}

and

if post publish date < 24 hours {
echo 'This post is published in last 24 hours!';
}

else { don't show nothing}

So how can I check this and show in post in list view (default.main.php) by adding some short code?

I'll be very grateful for your help with this thread!
Best regards!
Adam