in pokemon platinum how do u know when riolu will evolve

[pokeball]

how do you know when riolu will evolve in pokemon platinum

[Justin]

Riolu is a Time sensitive friendship evolution. Have it gain a level when it loves you, and during the day, and it will evolve to lucario.

To know how happy it is you can check the friendship app:

#06 Friendship Checker
A very useful application that you get early in the game. All the Pokemon in your party are displayed on the screen, bouncing around. By placing the stylus on the image of a particular Pokemon, it will show its affection/friendship/happiness level with a simple scale: 0 Hearts means its indifferent or simply doesn’t like you, 1 little heart means it cares, 2 little hearts means it likes you a bit and 2 Big hearts means it really like you.

Obtained: In Eterna City Poke Center, talk to the Girl closest to the door.

Pokemon Platinum Poketch Applications Guide

Check this guide for info on how to raise happiness of pokemons:

Pokemon Platinum Happiness Guide

Also read here for information on special evolutions:

Pokemon Evolution 200

Have fun evolving your pokemon!