As Pokémon Gold & Silver introduced the concept of time into the Pokémon games, and as such, the remakes; HeatGold & SoulSilver also make use of events such as these. The events are as follows:

Daily Events

Swarms

Every day, if you listed to Professor Oak's Pokémon Talk radio show, you will learn of a new swarm within the regions of Johto & Kanto. These Pokémon are usually incredibly rare or non existant within the locales so this is a perfect way to obtain the Pokémon. Go to the route specified to find the Pokémon The Pokémon options are enhanced after you obtain the National Dex

Click here for further details on Swarms

Lottery - Goldenrod City

In the Goldenrod Radio Tower, you will discover aty the reception that a Lottery is going on daily. This lottery provides 5 numbers and you need to have any of your Pokémon's IDs match up to the numbers in order to win. The more numbers matched, the better the prize. The top prize is a Master Ball

Seals - Olivine City

After you have received the Seal Case for healing the Miltank in the MooMoo Farm on Route 38, you can go to a house in Olivine where this girl will give you three different Seals every day

Buena's Password - Goldenrod City

After you have received the Blue Card from Buena's Assistant, at several points through the day (2am, 5am, 8am, 11pm, 2pm, 5pm, 8pm, 11pm), Buena's Password radio show will give out a question. You then need to go to Goldenrod's Radio Tower and meet Buena and give her the answer. She will give you three choices and if you select the correct one, you will receive points that you can later exchange form prizes

Vocabulary - Route 16

In the lone house in Route 16, you will find an old man. Each day, he will provide a new word for you to add to your vocabulary.

Pokéathlon Dome - Prize Counter

In the Pokéathlon Dome, there is a special counter that allows you to exchange your Prize Points for a variety of items. However, the items change each day so you should keep checking back for the item you want. The items are as follows:

Monday;
Red Apricorn; 200P
Blue Apricorn; 200P
Green Apricorn; 200P
MooMoo Milk; 100P
Moonstone; 3000P
Rare Candy; 2000P
Full Restore; 500P
King's Rock; 3000P
Sun Stone; 3000P
Water Stone; 2500P
Shiny Stone; 3000P
Dusk Stone; 3000P
Tuesday
Yellow Apricorn; 200P
Pink Apricorn; 200P
White Apricorn; 200P
MooMoo Milk; 100P
Fire Stone; 3000P
PP Up; 1000P
Full Restore; 500P
Metal Coat; 2500P
WaterStone; 2500P
Water Stone; 2500P
Dusk Stone; 3000P
Dawn Stone; 3000P
Wednesday;
Blue Apricorn; 200P
Pink Apricorn; 200P
Black Apricorn; 200P
MooMoo Milk; 100P
Water Stone; 2500P
Heart Scale; 1000P
Full Restore; 500P
Dragon Scale; 2500P
ThunderStone; 2500P
Moonstone; 3000P
Shiny Stone; 3000P
DawnStone; 3000P
Thursday;
Yellow Apricorn; 200P
Pink Apricorn; 200P
White Apricorn; 200P
MooMoo Milk; 100P
ThunderStone; 2500P
PP Up; 500P
Full Restore; 500P
King's Rock; 3000P
Fire Stone; 2500P
Leaf Stone; 2500P
Shiny Stone; 3000P
Dusk Stone; 3000P
Friday;
Red Apricorn; 200P
Yellow Apricorn; 200P
Green Apricorn; 200P
MooMoo Milk; 100P
Metal Coat; 2500P
Nugget; 500P
Full Restore; 500P
Dragon Scale; 2500P
Water Stone; 2500P
SunStone; 3000P
Dusk Stone; 3000P
Dawn Stone; 3000P
Saturday;
Green Apricorn; 200P
White Apricorn; 200P
Black Apricorn; 200P
MooMoo Milk; 100P
Leaf Stone; 2500P
Rare Candy; 2000P
Full Restore; 500P
Metal Coat; 2500P
ThunderStone; 2500P
Shiny Stone; 3000P
Dusk Stone; 3000P
Dawn Stone; 3000P
Sunday;
Red Apricorn; 200P
Blue Apricorn; 200P
Black Apricorn; 200P
MooMoo Milk; 100P
King's Rock; 3000P
Heart Scale; 1000P
Full Restore; 500P
Nugget; 500P
Sun Stone; 3000P
Fire Stone; 2500P
Shiny Stone; 3000P
Dawn Stone; 3000P
 

Goldenrod Underground

Days: All Days

The Goldenrod Underground is unique in that it has three counters for three different shops/utilities to go in. However, these utilies are diffirent and appear on different days. They are as follows

Bargain Shop: Monday Mornings
Hairdresser - Older Brother: Tuesday, Thursday, Saturday
Hairdresser - Younger Brother: Sunday, Wednesday, Friday
Herb Shop: Saturday, Sunday

Multiple Times A Week

Bug Catching Contest

Days: Tuesday, Thursday & Saturday

On Tuesdays, Thursdays & Saturdays, if you go to the National Park, you will discover that the Bug Catching Contest is in effect. This contest allows you to capture special Bug type Pokémon and try to win by catching the best Pokémon

Click here for further details on the Bug Catching Contest

SS Aqua

Days: Wednesday/Sunday (Vermillion to Olivine), Monday/Friday (Olivine to Vermillion)

Once you have the SS Ticket and have already been to Kanto, you will discover that the SS Aqua makes return trips between Johto & Kanto once a week from each port. The trip to Kanto and the trip to Johto both have a different batch of trainers on it.

Rival Rematch - Indigo Plateau

Days: Monday & Wednesday

After you and your rival have teamed up against Clair & Lance in the Dragon's Den, your rival will begin appearing in the Indigo Plateau. If you go up to the second floor, he will come in and challenge your. This can happen twice a week so it's good training

Silver Sneasel
Lv. 55
Crobat
Lv. 58
Magneton
Lv. 55
Gengar
Lv. 58
Alakazam
Lv. 56
Meganium
Lv. 60
Silver Sneasel
Lv. 55
Crobat
Lv. 58
Magneton
Lv. 55
Gengar
Lv. 58
Alakazam
Lv. 56
Typhlosion
Lv. 60
Silver Sneasel
Lv. 55
Crobat
Lv. 58
Magneton
Lv. 55
Gengar
Lv. 58
Alakazam
Lv. 56
Feraligatr
Lv. 60

Once A Week

Gym Leader Rematches

At various points each week, after you have found the Gym Leaders away from the gym at other points, the gym leaders of Johto & Kanto are available to rematch. If you call them up at specific times each week, they will go to the Saffron CityFighting Dojo and remain there until you battle them

Click here for further details on the Gym Leader Rematches

Lapras - Union Cave

Day: Friday

Every Friday, you will be able to find Lapras hidden within the Union Cave's Basement. Even if you capture it the previous week, another will appear the Friday afterwards. You need Surf to reach the Lapras so you cannot get it until after you have beaten Morty.

Lv. 20

Clefairy Dance - Mt. Moon

Day: Monday 20:00 - 23:59

Ever Monday Night, if you go up to the top of Mt. Moon, you will find a group of Clefairy dancing in the moonlight. After observing the dance for a while, they will spot you and flee. One of them will leave a MoonStone behind for you to take

Hoenn Sound

Days: Wednesday

After obtaining the National Dex, every Wednesday, the radio show Hoenn Sound appears on the Pokémon Music channel. If you play this music while in certain areas of Kanto & Johto, Pokémon usually indigenous to the Hoenn region will start to appear in the wilrd

Click here for further details on Hoenn Sound

Sinnoh Sound

Days: Thursday

After obtaining the National Dex, every Thursday, the radio show Sinnoh Sound appears on the Pokémon Music channel. If you play this music while in certain areas of Kanto & Johto, Pokémon usually indigenous to the Sinnoh region will start to appear in the wilrd

Click here for further details on Hoenn Sound