The following furniture will change with the season.

Do note that those changes are arbitrary and may not happen at the same time each year, if at all.

Chair+Desk

Chabudai Set

The "Chabudai Set" (ちゃぶ台セット) will change depending on the season:

During the saury season, food will change depending on the secretary (see here).

Season	Look	Picture
Normal	Fish
Saury	Saury

Admiral's Mahjong Table

The "Admiral's Mahjong Table" (提督の麻雀卓) will change depending on the season:

Season	Look	Picture
Cold Seasons	Snow patterns kotatsu futon & sake
Setubun	Setsubun-themed kotatsu futon (the cat's tail is animated when clicked on)
Hot Seasons	No kotatsu futon & sake

Hot Spring Hinoki Bath

The "Hot Spring Hinoki Bath" (温泉檜風呂) will change depending on the season:

Season	Look	Picture
Normal	Sake
Spring	Sakura & tea
Rainy season	Hydrangea
Summer	Half full
Fall	Red maple leafs & tea / susuki & sake

Hot Spring Stone Bath

The "Hot Spring Stone Bath" (温泉岩風呂) will change depending on the season:

Season	Look	Picture
Normal	Sake
Spring	Sakura /& sake
Rainy season	Hydrangea
Summer	Sunflowers
Fall	Red maple leafs /& sake / susuki
Winter	Nanten & mikans

Admiral's New Year Spending Spree

The "Admiral's New Year Spending Spree" (年末年始の提督大奮発) will change depending on the season:

Season	Look	Picture
New Year Normal	Ozoni
New Year 2	Rice porridge with seven herbs
New Year's Eve	New Year's Eve soba noodles

Café Table Set

The "Café Table Set" (Caféテーブルセット) will change depending on the season:

Season	Look	Picture
Normal	Pancakes
Zuiun Festival	Pancakes & Zuiun
Setsubun	Setsubun beans & cakes
Valentine's Day	Chocolate love cake
White Day	White Day cookies
Halloween	Pumpkin cakes
Christmas	Xmas cakes
Autumn	Mont Blanc

Secretary and Admiral's Desks Type 2 / French Ships la Table

The "Secretary and Admiral's Desks Type 2" (秘書艦と提督の机二型) and French Ships la Table (フランス艦 la table) will change depending on the season:

During the White Day season, food will change depending on the secretary (see here).

Season	Secretary and Admiral's Desks Type 2	French Ships la Table
Normal (old)
Normal (new)
White Day

Coastal Defense Ships' General-purpose Circular Desk

The "Coastal Defense Ships' General-purpose Circular Desk" (海防艦の汎用円形机) will change depending on the season:

Season	Look	Picture
New Year	Ozoni, Kadomatsu, and ink writing
New Year 2	Rice porridge with seven herbs
Setsubun	Setsubun beans & masks
Valentine's Day	Chocolate making
Hinamatsuri	Hinamatsuri
White Day	White Day cookies eating
Spring	Spring buquet and mochis with orange juice
Boy's Day	Boy's Day set
Rainy Season	Rainy season set
Summer	Summer set with whater melon
Autumn	Chestnuts cracking and writing/drawing
Saury	Saury flag and food
Christmas	Wmass foods and decorations
New Year's Eve	New year soba

Mikans and a Custom-made Naval Base Chabudai Table

The "Mikans and a Custom-made Naval Base Chabudai Table" (蜜柑と特注鎮守府ちゃぶ台) will change depending on the season:

During the New Year season, food will change depending on the time of day and secretary (see here).

Season	Look	Picture
Setsubun	Setsubun beans & maki
Valentine's Day	Valentine's sweets
White Day	White sweets
Spring/Summer	Strawberies sweets
Fall & Winter	Green tea & fried rice?
Saury	Saury & soup
Christmas	Strawberries cake
New Year	New's year soba

Admiral and Ooyodo Secretary Desk

The "Admiral and Ooyodo Secretary Desk" (提督と大淀秘書机) will change depending on the season:

Season	Look	Picture
Rainy Season	Hydrangeas, cakes & tea
Summer	Sunflowers, strawberry mochi & green tea
New Year	Forsythia & red cosmos, cakes & tea
Fall	Cosmos & ? , mikans & tea
Xmas	Poinsettia, shtrudel & coffee

Windows+Curtains

Naval Base Counter Bar

The Naval Base Counter Bar's food will change depending on the season.

See here.

Mini Kadomatsu and Zodiac Window

The "Mini Kadomatsu and Zodiac Window" (ミニ門松と干支の窓) will change depending on the year:

Year	Picture
Ox
Tiger	200px
Rabbit
Dragon
Snake
Horse

Submarine Squadron Window

The "Submarine Squadron Window" (潜水艦隊の窓) will change depending on the season:

Season	Look	Picture
New Year's Eve	New Year's Eve soba noodles
New Year	New Year's bouquet & Kadomatsu
New Year 2	New Year's bouquet & rice porridge with seven herbs
Setsubun	Hiiragi Iwashi with white flowers, & Setsubun beans
Valentine's Day	Bouquet & Valentines's gifts
White Day	Bouquet & White Day gifts
Spring	Sakura bouquet and spring mochis
Rainy Season	Hydrangea & Tru Teru Bonzou
Summer	Sunflowers & ice
Autumn	Mapple leafs & chestnuts
Children's Day	Japanese anemones & Children's Day set
Saury	Kalanchoe & Saury flag
Christmas	Poinsettia & Xmass decorations, cakes and gifts

Haruna's White Window

The "Haruna's White Window" (榛名の白い窓) will change depending on the season:

Season	Look	Picture
Autumn	Mapple leafs & tea and buns
Winter	Anemone coronaria & coffee
Spring	Magnolia & tea
Spring	Sunflowers, ice creams & lemonade

Mainstay of Mainstay Seasonal Window

The "Mainstay of Mainstay Seasonal Window" (主力オブ主力な季節の窓) will change depending on the season:

Season	Picture
New Year
Setsubun
White Day
Halloween
Fall
Xmas
New Year's Eve

Decoration

Japanese Cherry Blossom Arrangement

The "Japanese Cherry Blossom Arrangement" (桜の和のアレンジメント) will change depending on the season:

State	Notres	Picture
Buds
50% in bloom	Animated when clicked-on
75% in bloom	Animated when clicked-on
Full bloom	Animated when clicked-on
Leafed blossom	Animated when clicked-on
Leafed

Large Flower Arrangement

The "Large Flower Arrangement" (大型生花アレンジメント) will change depending on the season:

Season	Look	Picture
Winter	Poinsettia, winter rose, sweet alyssum
Spring	Hanami bouquet: tulips, myosotis, achillea filipendulina, sakura
Rainy season	Hydrangeas
Summer	Sunflowers
Fall	Dahlia, cosmos, bellflower, lady's mantle, kudzu, salvia

"Offshore Waves" Personal Belongings Shelf

The "Offshore Waves" Personal Belongings Shelf (「沖に立つ波」私物棚) will change depending on the season:

Season	Picture
Normal
New Year

7th Destroyer Squadron Personal Belongings Shelf

The "7th Destroyer Squadron Personal Belongings Shelf" (七駆の私物棚) will change depending on the season:

Giggles and plays a voiceline when clicked on.

Season	Look	Picture
New Year	New Year decorations
Setsubun	Setsubun beans, panel, and bag
White Day	White Day cookies and tea
Rainy Season	Hydrangeas and teru teru bonzou
Summer	Sunflowers and swimming equipment
Autumn	Sweet potatoes, autumn leafs, susukis
Xmas	Xmas decorations
New Year's Eve	New Year's Eve decorations