The date header and date footer can contain date and time vars. More info on the available vars. If you want to get started quickly, use "%x" to format the date. The language which is used to format the date, is determined by the locale-setting in the template.
In the date header, the template variable <%%daylink%%> is allowed to insert a link to the archive for that day. Note the double '%'! It's necessary to avoid %d to be expanded as the current day of the month. Also, if you just want to add a '%' character somewhere, you should also put it twice ('%%') or it will be gone on your website.
Sample for date header:
<div class="day"> <h1>%d %B</h1>
Sample for date footer:
</div>
And another example for the date head using daylink
<div class="day"> <h1>%d %B</h1> <a href="<%%daylink%%>">(archive)</a>