Allow users to add their friends or families birthdays

Play music in the background of a countdown

July 4th

Presidential Inauguration 2020

Mobile World Congress; 27 Feb-2 March, Barcelona
https://www.mobileworldcongress.com/

Release dates for Video games (Console, PS2, PS3, PS4, XBox, Nintendo, 3DS, Wii, Xbox One, Xbox 360, PC, Mac, Steam, Vita)

It's cool being able to countdown to when a day starts, but as far as I'm aware there's no way to countdown to an exact time during a day, like 3:30pm on 7th of December as a random example.

For Google Android

This is a beautiful count down website. Is there a way to embed one of these count-downs into my website?

Instead of having just days to have a tab for today's date

var today = new Date();
var dd = today.getDate();
var mm = today.getMonth()+1; //January is 0!
var yyyy = today.getFullYear();

if(dd<10) {
dd='0'+dd
}

if(mm<10) {
mm='0'+mm
}

today = mm+'/'+dd+'/'+yyyy;
document.write(today);

Allow users to track the number of days since a relationship started with (when they met or started going out with) a friend, girlfriend, boyfriend, fiance, husband, wife etc.

Spring break is everyone's favorite spring time.

TV show important dates such as season premieres, finales

I think that an easy way to customize an event, without having to persist the details per user, would be to use query parameters to customize the event. For example, if I wanted to create a countdown to the Anthem 5K Fitness Classic, a road race in Louisville, KY and the start of the Louisville Triple Crown of Running, I could specify the following URL:

http://days.to/until/7-march?description=Anthem%205K%20Fitness%20Classic

This would display the countdown as it does today, but would display the specified description as well. I am sure that other query parameters could be specified to expand the possibilities.