Revision 9

Overview

inZOI 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.

28-Day Calendar System (v0.7.0)

The v0.7.0 update (March 26, 2026) added a full in-game calendar organized into 28-day months. The calendar serves as a centralized hub for tracking the passage of time and all important dates in a Zoi's life.

What the Calendar Displays

The calendar UI shows multiple layers of information at a glance:

Recurring Holidays

Players 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.

Seasonal Holidays

Four seasonal holidays were added alongside the calendar system. Each season has a dedicated celebration:

When a seasonal holiday arrives, festivals are held across the game's cities. See the Seasonal Events article for full details on each celebration.

Day Length Settings

The 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.

Changing 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. The playback speed controls (1x to 4x) at the bottom-left of the screen provide additional time acceleration on top of the day length setting.

Seasons

inZOI features four seasons: Spring, Summer, Fall, and Winter. Each season lasts 7 in-game days. At the default day length setting, a full season takes approximately 10.5 hours of real time. 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.

Seasonal behavior differs by city. Dowon experiences all four seasons with noticeable temperature shifts: warmer summers and colder winters. Bliss Bay maintains a warm climate year-round, reflecting its Southern California inspiration. Cahaya has a tropical climate without cold winters.

Temperature changes affect Zoi behavior and health. Zois automatically adjust their clothing based on the current temperature. 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.

Life Stage Durations

Zois age automatically as in-game days pass. Each life stage lasts a set number of days:

A Zoi's total natural lifespan spans 100 in-game days from Newborn to the end of the Senior stage. Players can disable aging entirely in Game Options > Simulations (added in v0.1.4), or speed up aging by reducing the day length.

Birthday System

The 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.

How Aging Works With Birthdays

When a Zoi's birthday arrives, they advance to their next life stage through one of two paths:

1. Blowing 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.

2. 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.

Birthday Parties

Birthday parties are a type of social event that players can organize to celebrate a Zoi's aging milestone. To throw a birthday party:

1. Open the Smartphone (P key) and tap the Events app.

2. Find an open time slot on the Zoi's schedule (minimum 2-hour block).

3. Select Make Event and choose Party as the event type.

4. Name the party, set its duration, and choose a location.

5. Invite up to 10 guests, set the dress code, and choose recommended/prohibited activities.

6. Decorate the venue before guests arrive for a smoother party experience.

Birthday Party Activities

During a birthday party, an activity list appears with optional tasks:

• Greeting guests as they arrive.

• Blowing out candles: The birthday Zoi blows out candles on their cake, which triggers the age-up to the next life stage.

• Smashing a pinata: An interactive pinata can be set up at the party. Breaking it releases candy for party guests to collect.

• Gift-giving from invited guests.

• Taking a group photo with party attendees.

Guests arrive automatically once the event starts. Completing these activities enhances the party experience, though they are not mandatory.

Party Customization

When setting up any party, you can configure which activities guests are encouraged or prohibited from doing:

Pregnancy Tracking

When 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 grows. The calendar display helps players plan around the arrival of a new family member, ensuring they can prepare the home and adjust schedules before the baby is born.

Related Features