In short:
I need a countdown timer to a specific day (Thursday) at a specific time (9 am) that recurs weekly and resets the value when it ends. It should look like the Countdown Timer web part in SharePoint, so it should display days, hours, minutes, and seconds (with a zero in front of each when appropriate).
Additional information:
Using a simple countdown feature (in conjunction with a Timer control) doesn't seem to work because the number of milliseconds in a week (604800000) seems to be outside the scope/maximum of either the timer control or the Text function. And as a result, the output defaults to "01:23:59:59", which makes it seem like the max is 2 days (which can't be true). Here is what I used in the Text property of Timer1:
Text(Time(0, 0, (Timer1.Duration-Timer1.Value)/1000), "dd:hh:mm:ss")
Also, it doesn't seem like the countdown is stored/saved between refreshing the app. So, this all led me to use the DateDiff() function which wouldn't need to store a countdown value; it would just subtract Now() from the target date (Thursday at 9 am). But I couldn't figure out how to turn the target date into a variable that could arithmetically play with Now().
Spent a lot of time looking into this to no avail. Thanks everyone!