The variables in the code are #currentDate# and #tomorrow#
I can't figure out how to bind the current date to variable to use it in the URL.
That you really can't do, as WebParser can't use Dynamic Variables.
The only way I can think of to do it would be to get the date components you want from Time measures then have a OnLeftMouseUpAction on some meter that when clicked, would use !WriteKeyValue to set the URL as you desire, then it would refresh the skin. It would really HAVE to be manual, in that it would require you clicking on something to fire it off however, or you will get into an endless loop. Even then, Date+1 is going to be tricky unless you jump out to Lua, as the Time measure only returns a formatted string for the current date, and there is no easy way to do math with that in Rainmeter.