Don't know what you want to do, but either way check the reference Time & Date section:

day()
hour()
millis()
minute()
month()
second()
year()

For most timing issues you would use millis(). For an actual timestamp you use the others or search the forum for many other ways to generate a timedate-stamp

You also have a class Ball.

What you want is the time or

• day()
• hour()
• millis()
• minute()
• month()
• second()
• year()

stored within the class Ball.

Thus each ball has it's time.

In the constructor additionally have

1.   int s = second();  // Values from 0 - 59
     int m = minute();  // Values from 0 - 59
     int h = hour();    // Values from 0 - 23
   

or similar.

Greetings!