Chronoverse

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pub version pub points zero dependencies platforms BSD 3-Clause license

Chronoverse is an all-in-one calendar and date toolkit for Flutter. One import gives you calendars, pickers, schedules, planners and a complete date/time function library, with zero third-party dependencies, full theming and 14 built-in languages.

import 'package:chronoverse/chronoverse.dart';

Contents

Why Chronoverse
Every calendar style Month with swipe, expandable week ↔ month, two-week, vertical scrolling (booking), year overview, week strip, day/week schedule, agenda list, activity heatmap.
Every selection style Single, multiple, range (with max length and presets), or none. Freeze, read-only, and disabled states.
Type or pick Masked text field with validation and natural language ("next friday", "in 3 days", "25 dec"). Dialogs, bottom sheets, wheels, quick year/month grids.
Planner Multicolour event cards in 5 shapes, long-press drag of notes and events onto any day.
Schedule Day / 3-day / week time grid, overlap layout, drag to move, drag edge to resize, work hours, blocked slots, now line.
Toolbox 80+ ready functions in Chrono: date math, business days, age, leap years, ISO weeks, formatting, parsing, relative time, calendar conversions, time zones, moon phase and more.
Events Attendees, organizer, reminders, status, visibility, busy/free, event types, meeting link, time zone, recurrence with exceptions, iCalendar (.ics) import/export.
Calendars Gregorian, Hijri, Persian (Solar Hijri), Indian National (Saka), Buddhist, Julian; Julian Day, Unix and spreadsheet serial numbers.
Lightweight Pure Dart core (package:chronoverse/core.dart) usable without Flutter UI. No dependencies at all.
Cross-platform Android, iOS, web, macOS, Windows and Linux. Developed and tested on macOS and Windows as well as Linux.

Showcase

Month, planner, booking and pickers Schedule, agenda, year and strip Dialogs, sheets, quick picker, dark mode Theming, toolbox, collapsed week, dark schedule

The example app contains every screen above. Run it with cd example && flutter run.

Installation

flutter pub add chronoverse

or add it to pubspec.yaml:

dependencies:
  chronoverse: ^1.0.0

No platform setup, no localization delegates, no initialization call. It works the same on macOS, Windows and Linux development machines. Step-by-step instructions for each platform are in the Installation Guide (PDF).

Quick start

ChronoCalendar(
  onDaySelected: (day) => print(day),
)

A range picker that collapses to a week and shows events:

final controller = ChronoCalendarController();

ChronoCalendar(
  controller: controller,
  mode: ChronoSelectionMode.range,
  expandable: true,                    // drag the handle or tap to expand/collapse
  events: myEvents,                    // List<CalendarEvent>
  availability: DateAvailability(disablePast: true, disabledWeekdays: {DateTime.sunday}),
  maxRangeDays: 14,
  onRangeSelected: (range) => print(range), // null while only the start is picked
);

// Drive it from code
controller.showWeekOf(DateTime(2026, 12, 21)); // collapse to that week
controller.expand();                          // back to the full month
controller.jumpTo(DateTime(2027, 3));          // any month
controller.freeze();                          // look but don't touch

Widgets

Widget What it is
ChronoCalendar Month / two-week / week calendar, swipe between pages, expandable, quick year→month picker in the header, keyboard arrows, week numbers, markers or chips, drag & drop target.
ChronoVerticalCalendar Continuous vertical months, ideal for bookings; dayLabelBuilder puts prices or notes under each day.
ChronoYearView Twelve mini months with event shading.
ChronoWeekStrip Horizontal scrolling day strip.
ChronoScheduleView Time grid for 1–7 days with drag to move and resize.
ChronoAgendaView Grouped list of upcoming events.
ChronoHeatmap Activity heatmap over weeks.
ChronoDateField Text field with mask, validation, natural language and a picker button.
ChronoDateWheelPicker Day / month / year wheels in any order, leap-year aware.
ChronoMonthPicker, ChronoYearPicker Quick month and year grids.
showChronoDatePicker Date dialog or bottom sheet with a "type it" mode.
showChronoRangePicker Range dialog or sheet with presets ("Last 7 days", "This month"…) and a maximum length.
showChronoMultiDatePicker Pick any set of days.
showChronoWheelPicker Wheels in a bottom sheet.

Typed input

ChronoDateField(
  pattern: 'dd/MM/yyyy',          // mask and validation follow the pattern
  firstDate: DateTime(2000),
  lastDate: DateTime(2030),
  onChanged: (date) => print(date), // null while invalid
);

Accepts 25/12/2026, 25-12-2026, 25.12.26, today, tomorrow, next friday, in 3 weeks, 2 days ago, end of month, 25 dec, 5th of march and more.

Planner: cards and drag & drop

ChronoCalendar(
  events: events,
  markerStyle: ChronoMarkerStyle.chips,                      // dots, bars or chips
  chipStyle: const ChronoChipStyle(shape: ChronoChipShape.pill),
  theme: const ChronoThemeData(cellHeight: 92),
  onDrop: (day, data) { /* add a note or move an event */ },
);

// Anything can be dragged onto a day:
ChronoDragItem<String>(data: 'Pay rent', child: Chip(label: Text('Pay rent')));

Event cards inside the calendar are draggable too: drop them on another day to reschedule. Chip shapes: rounded, pill, square, accentBar, outlined. Each event has its own colour.

Schedule

ChronoScheduleView(
  date: DateTime.now().startOfWeek(),
  numberOfDays: 7,
  events: events,
  startHour: 7,
  endHour: 21,
  workHours: (9, 18),
  snap: const Duration(minutes: 15),
  onEventMoved: (occurrence, start, end) { /* save */ },
  onSlotTap: (time) { /* create */ },
);

Custom cells

Every cell can be replaced or decorated:

ChronoCalendar(
  dayBuilder: (context, state) => state.isWeekend ? MyWeekendCell(state) : null, // null = default
  dayLabelBuilder: (context, day) => Text('\$${price(day)}'),
);

The Chrono toolbox

All functions are static on Chrono, and also available as extension methods on DateTime. Import package:chronoverse/core.dart to use them without any widgets.

Chrono.isLeapYear(2028);                         // true
Chrono.daysInMonth(2024, 2);                     // 29
Chrono.addMonths(DateTime(2024, 1, 31), 1);      // 2024-02-29 (clamped, never overflows into March)
Chrono.age(DateTime(2000, 2, 29));               // correct for leap-day birthdays
Chrono.difference(a, b);                         // 3y 2m 5d
Chrono.addBusinessDays(DateTime.now(), 10, holidays: myHolidays);
Chrono.weekNumber(DateTime.now());               // ISO 8601 week
Chrono.format(DateTime.now(), 'EEEE, do MMMM yyyy', locale: 'fr');
Chrono.parse('25/12/2026', 'dd/MM/yyyy');
Chrono.parseNatural('next friday');
Chrono.timeAgo(someDate, locale: 'es');          // "hace 3 días"
Chrono.countdown(launchDate);                    // (days: 12, hours: 4, minutes: 10, seconds: 55, …)
Chrono.toHijri(DateTime.now());                  // and toPersian, toIndianNational, toBuddhist…
Chrono.toUnix(DateTime.now());
Chrono.toSpreadsheetSerial(DateTime.now());
Chrono.easter(2027);
Chrono.moonPhaseName(DateTime.now());
Full list of toolbox functions

Now and basics · now today tomorrow yesterday isLeapYear daysInMonth daysInYear weekNumber weeksInYear quarter dayOfYear isWeekend isPast isFuture isSameDay isValidDate isValidYmd

Arithmetic · addDays addWeeks addMonths addYears addBusinessDays businessDaysBetween daysBetween weeksBetween monthsBetween yearsBetween difference age nextAnniversary datesBetween monthMatrix easter nthWeekday

Format and parse · format parse parseNatural timeAgo formatDuration formatHms countdown monthNames weekdayNames

Conversions · toHijri toPersian toIndianNational toBuddhist toJulianCalendar fromCalendar toJulianDay toUnix fromUnix toUnixMillis fromUnixMillis toSpreadsheetSerial fromSpreadsheetSerial atOffset convertOffset toIso fromIso

Time of day · minutesOfDay isTimeBetween (works across midnight) roundTime partOfDay

Fun extras · zodiacSign chineseZodiac moonPhase moonPhaseName

DateTime extensions · dateOnly endOfDay isToday isSameMonth startOfWeek endOfMonth startOfQuarter nextWeekday nthWeekdayOfMonth daysUntil clampTo atTime isoWeekNumber and more.

Classes · DateRange DateDifference DateMath DateAvailability ChronoFormat RelativeTime NaturalDateParser CalendarConverter ZonedDateTime ChronoTimeZone RecurrenceRule CalendarEvent Schedule ICalendar

Events, recurrence and time zones

final standup = CalendarEvent(
  id: 'standup',
  title: 'Stand-up',
  start: DateTime(2026, 10, 19, 9, 30),
  end: DateTime(2026, 10, 19, 9, 45),
  timeZone: 'Europe/London',
  recurrence: RecurrenceRule.parse('FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR'),
  exceptionDates: [DateTime(2026, 12, 25)],
  attendees: [const EventAttendee(email: 'sam@example.com', name: 'Sam', response: AttendeeResponse.accepted)],
  reminders: [const EventReminder.minutes(10), const EventReminder.minutes(60, method: ReminderMethod.email)],
  meetingUrl: 'https://example.com/room/42',
  color: 0xFF5B5BD6,
);

standup.recurrence!.describe();                      // "Every week on weekdays"
events.occurrencesIn(DateRange.month(DateTime.now()));
Schedule.freeSlots(events.on(today), from: today.atTime(9), to: today.atTime(17), minLength: const Duration(minutes: 30));

final ics = ICalendar.encode(events);                // export .ics
final imported = ICalendar.decode(icsText);          // import .ics

final kolkata = ChronoTimeZone.get('Asia/Kolkata');
kolkata.convert(DateTime(2026, 10, 20, 19, 30), ChronoTimeZone.get('America/New_York'));

Time zones include daylight-saving rules for North America, Europe, Australia and New Zealand, with correct handling of the skipped and repeated hours. You can register any extra zone with ChronoTimeZone.register.

Theming

Everything is themeable: colours, day shape (circle, rounded, square, stadium), radius, cell size, padding, header height, text styles, marker size, animations. Set it once for the whole app:

MaterialApp(
  theme: ThemeData(
    colorSchemeSeed: Colors.indigo,
    extensions: const [ChronoThemeData(dayShape: ChronoDayShape.rounded, cellHeight: 48)],
  ),
);

or per widget with theme:. Light and dark mode follow your app automatically. ChronoThemeData.fromSeed(color) builds a full palette from one colour.

Languages

Built in: English, Spanish, French, German, Italian, Portuguese, Russian, Arabic (RTL), Hindi, Marathi, Chinese, Japanese, Korean and Turkish. Each locale knows its month and weekday names, first day of week, weekend days, date order, plural rules and native digits.

ChronoCalendar(locale: ChronoLocale.of('ar'), nativeDigits: true);

Add your own language with ChronoLocale.register(...). Nothing to set up in MaterialApp.

Freeze, enable, disable

Need How
Temporarily lock all interaction controller.freeze() / controller.unfreeze()
Show but don't allow changes readOnly: true
Disable the whole widget (greyed out) enabled: false
Disable specific days availability: DateAvailability(disabledDates: [...], disabledRanges: [...], disabledWeekdays: {...})
Only allow some days DateAvailability(enabledDates: [...])
No past / no future DateAvailability(disablePast: true)
Any custom rule selectableDayPredicate: (day) => ...
Limit range length maxRangeDays: 14
Limit navigation firstDay: / lastDay:

Problems this package solves

Common complaints with calendar widgets, and what Chronoverse does about them:

  • Month arithmetic overflows (Jan 31 + 1 month = March 3). Chronoverse clamps to the last valid day.
  • Daylight-saving bugs (a day that is 23 hours long breaks "add one day"). All date math is calendar-based, not duration-based.
  • Leap years (Feb 29 birthdays, Feb 29 + 1 year). Handled everywhere, including the wheels and age.
  • No quick way to jump years. Tap the header to pick a year, then a month.
  • Can't control the visible week from code. showWeekOf, expand, collapse, jumpTo.
  • Calendar height jumps between months. sixWeekMonths: true keeps it fixed.
  • Localization needs extra setup. It doesn't: 14 languages work with one parameter.
  • Slow with many events. Events are indexed per day once, not filtered on every cell build.
  • Range picker accepts blocked days in the middle. Ranges that cross unavailable days are rejected.
  • Hard to customise one cell. Builders return null to keep the default, so you only override what you need.
  • Broken in right-to-left, large text, or keyboard use. RTL, text scaling, arrow-key navigation and screen-reader labels are built in.
  • Dependency conflicts. There are none to conflict with.

Guides (PDF)

  • Installation Guide: requirements, macOS and Windows setup, adding the package, verifying, troubleshooting.
  • Integration Guide: every widget and function with code, theming, languages, events, time zones and best practices.

API reference: pub.dev/documentation/chronoverse.

Disclaimer and policies

Chronoverse is provided "as is", without warranty of any kind. Date, time, time-zone, calendar conversion, recurrence and every other calculation may contain errors. You are solely responsible for verifying all results before relying on them, especially for legal, financial, medical, religious, safety-critical or time-critical purposes. The authors and contributors accept no liability for any loss or damage arising from its use.

Please read the full documents before use:

By using this package you agree to these documents.

Author

Chronoverse is designed and developed by Sanket Santosh Vidya Manohar.

Found a bug or have an idea? Open an issue.

Copyright (c) 2026, Sanket Manohar. Released under the BSD 3-Clause License.

Libraries

chronoverse
Chronoverse: an all-in-one, dependency-free calendar and date toolkit.
core
Chronoverse core: pure-Dart date math, formatting, parsing, recurrence, calendar-system conversions, events and iCalendar.