You know how in mobile games you have those bonuses is you play the game a weak in a row. I came up with this monstrosity (widgets and saving will be done later):
I never used this “Today” API, but a simple algorithm like this one should work:
At first launch: StartDate = Today (variable must be saved)
Counter = 0 (variable must be saved)
Then, at each launch:
if ceil(Today - StartDate) != counter + 1 => reset as if first launch, because it means at least a day has passed without the game being launched.
else counter++
if counter == 6: the game has been launched each days for seven days. You can reset
Of course, if the game is not restarted, you need a way to detect that 24h passed since launch to do the “at each launch” part.