There are a few things in Ruby and Sapphire that only happen on a daily basis. These events don't show up as frequently as in Gold and Sapphire, or any Generation IV games or beyond for that matter. As well, you may find if your internal battery runs out or your game suffers from the Berry Glitch you can't undergo these events. Still, here are some you can check out, and the conditions for such:

Evolution

The Pokemon Eevee evolves on a timed basis. However, now "day" and "night" are a bit more confusing. As the clock is now minimal, and there are no visibly notable changes in the time of day, it goes as follows For Espeon, evolve between 12:00 PM-11:59 PM
For Umbreon, evolve between 12:00 AM - 11:59 AM

Slateport City Market

After beating the Elite Four, there is a chance every day that the Energy Guru of Slateport will offer all vitamins at half price over the television.

Lilycove Lottery

Every day the winning numbers for the lottery in Lilycove changes. Match the numbers to a Pokemon's trainer ID to win a prize.

Prize Picture Name
5 Digits Master Ball
4 Digits Max Revive
3 Digits EXP. Share
2 Digits PP Up
Shoal Cave

Twice per day the tides change in this mysterious cave off the coast of Mossdeep, and twice a day you can collect the spoils from within to get the items needed for a Shell Bell. You can also only find Pokémon like Snorunt in areas that are accessible only in low tide.

High tide:
9:00 PM - 2:59 AM
9:00 AM - 2:59 PM
Low tide:
3:00 AM - 8:59 AM
3:00 PM - 8:59 PM

Mirage Island

Every day the old man in Pacifidlog Town will look for Mirage Island, and the corresponding number to make it appear is regenerated. For more information on Mirage Island, click here.

 
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