To find the date when the triplets turn 13 years old, we simply add 13 years to their birthdate, February 14, 2029.

• $2029 + 13 = 2042$

So, they will turn 13 on February 14, 2042.

Would you like more details or further explanation?

Here are five related questions to expand on this:

1. How would you calculate the day of the week for February 14, 2042?
2. What is a leap year, and how does it affect dates in the long term?
3. How would the date change if the triplets were born on February 29, 2029 (leap year)?
4. How many leap years occur between 2029 and 2042?
5. How old will the triplets be in 2050?

Tip: Leap years occur every 4 years, except for years divisible by 100 but not 400.