A free program for Android, by Rubén Mayayo.

If you are trying to keep a time counter on your phone, the How Long Widget – Time Counter is the app you are looking for. It is a free, simple, easy-to-use time widget for your Android phone. You can use it as a simple time clock, to count the number of days, hours, minutes, and seconds since a particular date.

It is very easy to use. You just need to enter the date, the title, and the event you want to be counted. The app will show you the result in seconds. If you want to reset the counter, just tap the reset button.