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Calendar and Birthday System - Version 17 vs Version 18
Aug 6, 2026, 01:19 PM
Added the official explanation for summer's missing public holiday
Aug 17, 2026, 03:56 PM
Removed screenshots that did not depict this page's subject
11Overview22inZOI tracks time through a day-night cycle, a four-season rotation, and a life stage aging system. Each in-game day progresses from morning to night, seasons change every 7 days, and Zois age through 9 life stages over the course of 100 in-game days. The March 2026 update (v0.7.0) introduced a dedicated 28-day month calendar system that tracks holidays, birthdays, and pregnancy due dates. Players can throw birthday parties as social events to celebrate aging milestones, and the calendar provides a centralized view of all upcoming events.44Because each season lasts exactly 7 in-game days, one 28-day month covers a full annual cycle of Spring, Summer, Fall, and Winter. This design gives long-running save files a clear sense of rhythm. Every month, the same holidays return, birthdays arrive on schedule, and the world transitions through all four seasons in a predictable loop.6628-Day Calendar System (V0.7.0)88The v0.7.0 update (March 26, 2026) added a full in-game calendar organized into 28-day months. This update coincided with inZOI's one-year anniversary in Early Access. The calendar is a centralized hub for tracking the passage of time and all important dates in a Zoi's life. It can be accessed from the Smartphone or through the main HUD.1010What the Calendar Displays1312The calendar UI shows multiple layers of information at a glance:1514ElementDescriptionSeasonsThe current season and upcoming seasonal transitions are visible on the calendar. Each season lasts 7 in-game days, so one 28-day month covers exactly four seasons (one full year cycle).HolidaysFour seasonal holidays are marked on the calendar at fixed points: Spring Festival, Halloween Festival, Winter Festival, and Year-End Festival. These holidays trigger in-game festivals and celebrations.BirthdaysEvery Zoi's birthday is marked on the calendar, even if no social event is planned for that day. This makes it easy to keep track of when household members and known Zois will age up.Pregnancy Due DatesWhen a Zoi is pregnant, the expected due date appears on the calendar. Pregnancy lasts about three in-game days, with each day representing a different stage as the baby bump grows.SchedulesStandard Zoi schedules and important events are displayed, helping players plan activities around work shifts, school hours, and other commitments.Status UpdatesLife event notifications appear on the calendar alongside a status updates menu, giving players a quick summary of recent milestones like promotions, graduations, and relationship changes.1716How Months Map to Seasons1817The 28-day month is divided into four equal weeks of 7 days each. Each week corresponds to one season:2019DaysSeasonHoliday Window1 - 7SpringSpring Festival8 - 14SummerNo fixed holiday15 - 21FallHalloween Festival22 - 28WinterWinter Festival, Year-End Festival2221A pop-up notification announces the start of each new season. Because the calendar loops every 28 days, long-term saves experience a continuous cycle of seasonal change. Players who leave aging enabled will see their Zois pass through roughly three and a half full annual cycles over a 100-day lifespan.2322Recurring Holidays2524Players can set different holidays to recur on specific dates within the calendar. Once configured, these holidays disappear and reappear automatically as the save file progresses through time. This means that seasonal celebrations are not one-time occurrences; they come back each year cycle, giving long-term saves a sense of rhythm and tradition. Festival-themed items in Build Mode, including decorations and seasonal furniture, are tied to these recurring holidays and become available during the appropriate time window each cycle.2726Seasonal Holidays2928Four seasonal holidays were added alongside the calendar system. Each season has a dedicated celebration that triggers festivals across the game's cities. See the Festivals and Seasonal Events article for full details on each celebration.3130HolidaySeasonDescriptionSpring FestivalSpringMarks the beginning of the new year cycle with seasonal festivities, flower-themed decorations, and community gatherings in city parks.Halloween FestivalFallAutumn celebration with spooky-themed activities, pumpkin farming, pumpkin carving, trick-or-treating events, and ghost fish fishing. Cities are decorated with Jack-o'-lanterns and haunted props.Winter FestivalWinterWinter holiday celebration with seasonal cheer, themed snack booths offering candy canes and hot chocolate, gift booths with limited-edition building items, and ingredient booths for crafting cookies.Year-End FestivalWinterCloses out the year cycle with end-of-year festivities. Falls near the end of the 28-day month, giving players one last celebration before the calendar resets.3332When a seasonal holiday arrives, festival booths and special NPCs appear in designated areas across all three cities. Players can purchase festival-exclusive items, participate in seasonal activities, and earn unique rewards. Holiday costumes, accessories, and decorative items rotate in and out of availability based on the current season, encouraging players to revisit festivals each cycle.3433Summer is the one season without a public holiday, and the team confirmed in July 2026 that this is deliberate. Summer is positioned as the travel season: many people take special trips at that time of year, and the travel content in development is meant to fill the season the way holidays anchor the other three.3635Day Length Settings3837The length of one in-game day can be adjusted in Settings > Simulation > Length of Day. This setting controls how quickly real time translates into in-game time, which affects how fast aging, seasons, and daily routines progress. The default is 96 minutes, which is notably longer than most life simulation games and gives players time to explore the large in-game cities.4039SettingReal Time per In-Game DayReal Time per Season (7 days)Notes48 minutes48 min~5.6 hoursFastest option; aging and seasons progress quickly.96 minutes96 min (1 hr 36 min)~11.2 hoursDefault setting; balanced pacing for exploration and activities.4 hours4 hours~28 hoursSlower pace; significantly more real time per day for activities.24 hours24 hours7 real daysReal-time mode; one real day equals one in-game day.4341Changing day length affects how quickly time passes during gameplay but does not change the total number of in-game days in a life stage. A Zoi who lives for 100 in-game days will always live 100 days regardless of the day length setting. Shorter day lengths are ideal for players who want to experience life stage transitions quickly, while longer settings suit players who prefer to take their time with daily routines and exploration.4442Playback Speed Controls4644The time panel at the bottom-left of the screen provides additional speed controls on top of the day length setting:4846ControlSpeed MultiplierNotesPause0xFreezes all simulation. Useful for building and decorating.Slow1xBase speed; the game runs at the pace set by day length.Normal1.5xSlight acceleration above base. Good for everyday play.Fast3xSpeeds through routine periods like sleep or commuting.Very Fast4xRapid acceleration for skipping long stretches.Manual Maximum10xMaximum speed. Movement controls and autonomy toggling are disabled above 5x.5048These speed multipliers stack with the day length setting. For example, running 4x speed on the 96-minute day length means one in-game day passes in roughly 24 real minutes. Players who want to watch Zois live out their full 100-day lifespan quickly can combine a short day length with high playback speed.5149Seasons5351inZOI features four seasons: Spring, Summer, Fall, and Winter. Each season lasts 7 in-game days. With the 28-day calendar, one full month equals exactly one complete cycle of all four seasons. A pop-up notification announces the start of each new season, and the calendar marks the transition days clearly.5553Seasonal behavior differs by city. Dowon experiences all four seasons with noticeable temperature shifts: warmer summers and colder winters with snowfall. Bliss Bay maintains a warm climate year-round. This reflects its Southern California inspiration, so winter feels mild rather than harsh. Cahaya has a tropical climate without cold winters, keeping temperatures consistently warm across all seasons.5755Temperature changes affect Zoi behavior and health. Zois automatically adjust their clothing based on the current temperature when autonomy is enabled. Wearing clothing not suited to the weather can cause illness, requiring a First Aid Kit to recover. Players can manually change the weather through the Edit City menu, though manual changes revert to the default seasonal weather after one in-game hour.5957Seasons also affect available seasonal activities. Certain crops grow only in specific seasons for gardening, and the types of fish available change with the season for fishing. Snow in winter opens up winter-specific interactions in cities that experience cold weather, while summer unlocks beach activities in Bliss Bay.6159Life Stage Durations6361Zois age automatically as in-game days pass. Each life stage lasts a set number of days:6563Life StageDuration (Days)Cumulative DaysNewborn11Toddler23Child710Adolescent515Teenager419Young Adult1029Adult2049Middle-Aged1665SeniorUp to 351006765A Zoi's total natural lifespan spans 100 in-game days from Newborn to the end of the Senior stage. Seniors may pass away from natural causes before reaching the full 35 days, so the actual lifespan varies. At the default 96-minute day length, a full 100-day lifespan takes roughly 160 real hours of gameplay.6866Players can disable aging entirely in Game Options > Simulation (added in v0.1.4). With aging disabled, Zois remain in their current life stage indefinitely and do not age up on their birthdays. This is useful for players who want to keep a household at a specific stage without time pressure. Babies born while aging is disabled will stay as Newborns until the setting is re-enabled.7068Birthday System7270The v0.7.0 update overhauled how birthdays work in inZOI. Every Zoi now has a birthday marked on the 28-day calendar, and the aging process is directly tied to birthday celebrations. When a birthday arrives, the Zoi transitions to their next life stage, making birthdays meaningful gameplay milestones rather than just cosmetic markers.7472How Aging Works with Birthdays7674When a Zoi's birthday arrives, they advance to their next life stage through one of two paths:7876Blowing out candles during a birthday party: If the player organizes a birthday party social event, the Zoi blows out candles on a birthday cake to officially age up. This is the celebratory path that allows friends and family to participate. The moment the Zoi blows out the candles, the visual transition to the next life stage happens immediately.Spending a birthday alone: If no birthday party is planned, the Zoi still ages up when their birthday arrives. They simply transition to the next life stage without a social event. The birthday is still marked on the calendar for tracking purposes, and the Memory System records the milestone regardless of whether a party was held.8178Birthday Parties8380Birthday parties are a type of social event that players can organize to celebrate a Zoi's aging milestone. Planning a birthday party follows the same steps as any other social event but centers around the age-up ceremony. To throw a birthday party:8582Open the Smartphone (P key) and tap the Events app.Find an open time slot on the Zoi's schedule (minimum 2-hour block required).Select Make Event and choose Party as the event type.Name the party, set its duration, and choose a location. Hosting at your own home gives you the most control over the setup.Invite up to 10 guests, set the dress code, and choose recommended or prohibited activities.Decorate the venue before guests arrive for a smoother party experience. Placing a birthday cake, balloons, and a pinata ahead of time ensures the activities are ready to go once the event starts.8784Guests arrive automatically once the event begins. The host Zoi receives a notification when each guest shows up. Late arrivals are common, so starting with greeting activities gives everyone time to filter in. If the host is not present when the event timer runs out, the event may cancel automatically.8986Birthday Party Activities9188During a birthday party, an activity list appears with optional tasks. Completing these activities enhances the overall party experience:9390Greeting guests as they arrive at the venue.Blowing out candles: The birthday Zoi blows out candles on their cake, which triggers the age-up to the next life stage. This is the highlight of the party and the only activity tied to gameplay progression.Smashing a pinata: An interactive pinata can be set up at the party. Breaking it releases candy for party guests to collect. Note that the interaction prompt may display as 'turn on the heater' due to a known translation issue.Gift-giving from invited guests. Gifts are received automatically during the party.Taking a group photo with party attendees to commemorate the celebration. These photos are saved and can be viewed later.9592None of these activities are mandatory. The Zoi will still age up even if the only completed activity is blowing out candles. However, completing more activities contributes to a better overall event rating and creates stronger positive memories for attendees.9794Party Customization9996When setting up any party, you can configure which activities guests are encouraged or prohibited from doing. This customization applies to birthday parties as well as other social events:10198CategoryActivitiesIndoorMusic, TV, bathing, repairs, sleep, cleaning.FoodEating, cooking, coffee.HobbiesInstruments, dancing, writing, games, reading, workouts, photos.OutdoorFishing, gardening, stealing.ConversationHugging, kissing, romance, fighting, rudeness, kindness.103100Setting a dress code helps create a consistent atmosphere. For birthday parties, recommending festive or casual attire and prohibiting fighting or rudeness keeps the mood positive. Encouraging music, dancing, and food activities tends to produce the best results for celebration-themed events.104101Pregnancy Tracking106103When a Zoi becomes pregnant, the calendar automatically marks the expected due date. Pregnancy lasts approximately three in-game days, with each day representing a different trimester stage as the Zoi's baby bump visibly grows. The calendar display helps players plan around the arrival of a new family member. This keeps they can prepare the home, adjust schedules, and stock up on supplies before the baby is born.108105Newborns arrive at the end of the pregnancy period and immediately begin their 1-day Newborn life stage. The baby can be customized in the Create a Zoi appearance editor after birth. In the v0.7.0 update, baby Zois received several improvements: their needs were rebalanced, newborns are now born without teeth and gain them as they develop into Toddlers, and a new quick-clean interaction lets adult Zois tidy up after babies more efficiently.110107Tips and Tricks112109Check the calendar at the start of each play session to see what birthdays and holidays are coming up. Planning a birthday party one day in advance gives you time to decorate and invite guests.If you want to age up a Zoi quickly without a party, you can reduce the day length to 48 minutes and increase playback speed. The birthday will arrive faster, and the Zoi ages up automatically even without a celebration.For players who enjoy the social aspect, always keep birthday cakes and pinatas in your household inventory. Having these items ready means you can set up a party venue in minutes without needing to purchase them last-minute.Use the pregnancy due date on the calendar to time household preparations. Building a nursery, buying baby furniture, and adjusting work schedules all benefit from advance planning.Disabling aging in Game Options > Simulation is useful if you want to spend extra time developing skills, careers, or relationships before a Zoi moves to the next life stage. Re-enable it when you are ready to continue the aging cycle.In Dowon, dress your Zois in weather-appropriate clothing before each season change to avoid illness. The calendar's seasonal markers help you anticipate when the switch will happen.114111Related Features116113FeatureDescriptionFestivals and Seasonal EventsDetails on each seasonal holiday festival and real-world event.Life StagesFull breakdown of each age group's abilities, restrictions, and unlocks.Social EventsHow to plan parties, dates, and weddings.Time and SeasonsDetailed weather and seasonal mechanics.Memory SystemBirthday memories as life milestones.PregnancyFull guide to the pregnancy system and baby care.Update HistoryTimeline of all game updates and patch notes.March 2026 UpdateFull patch notes for v0.7.0, the anniversary update that introduced the calendar.
