Websites can't add widgets on iPhone. This uses Scriptable, a free app from the App Store, to draw the Paris countdown widget. It takes about two minutes, once.
Prefer no apps? Use Add to Home Screen on the countdown page instead: it gives you an icon that opens the countdown full screen. It isn't a live widget.
1
Install Scriptable (free) from the App Store.
2
Tap Copy widget script below.
3
Open Scriptable, tap + at the top right, paste, then tap the title and name it Paris. Tap Done.
4
On your Home Screen, press and hold an empty space, tap Edit, then Add Widget. Pick Scriptable, choose the small size and tap Add Widget.
5
While it wiggles, tap the new widget, set Script to Paris, then tap outside. Done.