Head into the right-hand building on the middle road running through Castelia City and you will see a clown. He will ask to see a certain type of Pokémon each day, and will reward you with berries.

New trainers and new items appear here every day!

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During the Spring and Summer months, Cynthia will appear in a house in Undella Town and will battle you once a day.

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After you have beaten the Pokémon League and obtained the National Dex, inside Twist Mountain is a Fossil Maniac who will give you a random fossil every day:

In Nacrene City, as soon as you have visited the Dream World enter the second house you come to when entering the City. A girl will start making you a new piece of furniture for your Dream World Home Area every day. After performing a Game Sync, these pieces of furniture will be available to buy online.

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After you have beaten the Pokémon League and obtained the National Dex, head to the Gamefreak Building in Castelia City and on the 22F the Gamefreak employee Shigeki Morimoto will battle you every day.

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In Driftveil City, enter the house directly West of the Pokémon Center and you will find a girl who requests to see a Pokémon with a different attack each day. She will reward you with a Heart Scale.

Enter the top-left building on the eastern-most street of Castelia City. Talk to the girl inside and she will massage one of your Pokémon everyday.

Enter the South-Western most building of Opelucid City and you will find a man who will give you a different Musical Accessory everyday.

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After defeating N at Ferris Wheel in Nimbasa City, a different trainer will appear there every day to battle you.

Different sports will be played at the Sports Hall in Nimbasa City at different times of the day, allowing you to battle different trainers there every day.

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Head to Opelucid City and to the house closest to the exit to Route 10 (Unova). This house contains two trainers who will battle you on a daily basis.

Head to Village Bridge and enter the second house along counting from the East. A girl will leave with her Patrat and can be found again on Marvelous Bridge. Every day she will play a game with you whereby you have to track her Patrat as it runs around with three others. Win the game and she’ll give you a Big Mushroom.

Head to the South-East of Pinwheel Forest and you'll find the Challenge Rock. Take a fighting-type Pokémon there everyday and interact with the rock and you'll manage to chip yourself away a Star Piece.

Next to the entrance to Tubeline Bridge on Route 8 (Unova) is a Lady who will give you a different item depending on the time of day you talk to her:

Swarms will be activated as soon as you defeat the Pokémon League and receive the National Dex. Swarms can occur anywhere across Unova and change randomly everyday at midnight. Enter the gates between routes and the scrolling text on the back wall will inform you if any swarming Pokémon have been spotted nearby.

On Route 13 (Unova) is a Treasure Hunter who will give you a different item that he has found every day:

Inside the Villa to the West of Undella Town you will find a trainer who will battle you every day. Every day another trainer will join in and battle you consecutively, up to the maximum six trainers.

On Village Bridge is a Chef who, once you have defeated him in battle, will ask you to talk to people on the bridge to take their food orders. After talking to everybody and returning to the Chef he will reward you will a random selection of berries.

On Village Bridge you will find a Fisherman who asks to see a certain Pokémon every day, which you have caught by fishing. Show him the correct Pokémon and he will reward you with a Dive Ball.

After you have defeated the Pokémon League, Bianca will take residence in Professor Juniper’s Lab in Nuvema Town. After you talk to her she will battle you every Saturday.

The stall in Castelia City will sell Casteliacones on Tuesdays during Spring, Summer and Autumn.

A wild Musharna will appear at the Dreamyard every Friday.

In Anville Town, every weekend new tourists appear in the town and will offer you random items to trade.

In Anville Town an old man will give you unclaimed items from the lost property store on a weekly basis:

Every Friday night, a large group of thugs on bikes will appear on Tubeline Bridge. Defeat Underling Morgan and Boss Jeremy and they'll name the group after the lead Pokémon in your party.