Download the latest version from here.

What is it?

It's basically the same as the Firefox extension Morning Coffee which opens certain predefined URLs depending on the current weekday or something. I'm using Vimperator and don't have a toolbar in Firefox, so I can't use Morning Coffee.
Additionally, morningtea should work with any browser, not just Firefox.

How does it work?

It's a very simple Perl script that reads ~/.morningtea (or any file you specify as an argument) which contains the commands to call your browser and pairs of URLs and some kind of date pattern that defines when to open them.

Browser commands

The first line in ~/.morningtea is called a single time when you start morningtea, meant to start the browser if it is not running. I use iceweasel, so mine looks like this:
[ -h .mozilla/firefox/*/lock ] || xtoolwait iceweasel
If lock file exists, iceweasel is already running; else run iceweasel through xtoolwait to block until the browser window appears.

The second line is the command that opens each URL. Again, mine:
iceweasel -new-tab '%url'
Every occurence of "%url" is replaced with the actual URL.
Note that there is no escaping done for you; you have to do this in the URL if necessary.

URLs and date patterns

1: http://www.example.org/news
Open link on every day.

3: http://www.example.org/lazy-news
Open link on every third day.

1-5/w: http://www.example.org/work
Open link on days 1 to 5 of each week, i.e. Mondays to Fridays.
Note that weekday numbers start with 1 (Monday) and end with 7 (Sunday).

1,10,20/m: http://www.example.org/stuff
Open link on the 1st, 10th and 20th of each month.

That's pretty much it. Syntax is quite forgiving; you can put newlines/tabs/spaces wherever you want, except inside the URL and in the date pattern. Spaces in URLs can be replaced by + or %20.
Everything that doesn't fit into this pattern is ignored.