FarsiCalendar App: Accurate Persian Dates, Events & Reminders

FarsiCalendar: The Complete Persian Date Converter### Introduction

FarsiCalendar is a specialized tool designed to convert between the Gregorian (Western) calendar and the Persian (Jalali/ Hijri Shamsi) calendar. The Persian calendar is a solar calendar used primarily in Iran and Afghanistan; it differs from the Gregorian calendar in year numbering, month lengths, leap year rules, and cultural context. FarsiCalendar aims to provide accurate conversions, account for historical and regional variations, and offer features like holiday lookup, time-zone adjustments, and developer-friendly APIs.

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Background: What is the Persian (Jalali) Calendar?

The Persian calendar—commonly called the Jalali calendar or Hijri Shamsi—is a solar calendar with roots in ancient Persian timekeeping and later calendrical reforms. It was refined during the 11th century under the astronomer Omar Khayyam and adopted in modern form by Iran in the early 20th century. Key characteristics:

• Solar-based: months follow the solar year, aligned to Earth’s orbit around the Sun.
• Year numbering: the Jalali year counts from the Hijra (the Muslim migration), but because the calendar is solar, its year number differs from the Islamic lunar Hijri calendar.
• Months: Twelve months — the first six have 31 days, the next five have 30 days, and the final month has 29 days in common years and 30 days in leap years.
• Leap years: Determined by a complex astronomical/algorithmic rule rather than the simple Julian/Gregorian pattern; modern implementations use well-tested algorithms to identify leap years accurately.

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Why Accurate Conversion Matters

Accurate date conversion is important for:

• Legal and governmental records in Iran and Afghanistan.
• Historical and genealogical research.
• Scheduling apps, calendars, event reminders, and international communication.
• Software localization and compliance with local business practices.
• Religious and cultural observances that rely on specific Persian dates.

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Core Features of FarsiCalendar

• Date conversion:
  • Convert Gregorian to Jalali (and vice versa).
  • Support for date ranges and batch conversions.
• Time handling:
  • Time-zone support (including Iran Standard Time and daylight saving adjustments where applicable).
  • Time-of-day preservation during conversion.
• Leap-year and edge-case handling:
  • Correctly identifies Persian leap years.
  • Handles historical dates and transitions.
• Localization:
  • Persian (Farsi) and English language support.
  • Numeral formatting (Eastern Arabic numerals vs. Western digits).
• Holidays and events:
  • Built-in database of Iranian and Afghan public holidays (fixed and variable).
  • Option to include religious observances and astronomical events.
• Developer tools:
  • REST API and client libraries (Python, JavaScript) for easy integration.
  • Examples and code snippets.
• UI/UX:
  • Clean, responsive calendar widget for websites and mobile apps.
  • Copy/share options and export to iCal/CSV.

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How Conversion Works — Algorithms and Examples

Most FarsiCalendar implementations use an algorithmic approach to convert dates. One common method is to convert both calendars to a single continuous day count (like the Julian Day Number) and then compute the target calendar date.

Example (conceptual steps):

1. Convert Gregorian date to a Julian Day Number (JDN).
2. Convert JDN to Jalali date using the Jalali epoch and month/day rules.
3. Adjust for time zones or time-of-day if needed.

Example conversions:

• Gregorian 2025-03-21 → Jalali 1404-01-01 (Nowruz — Persian New Year).
• Gregorian 2025-09-23 → Jalali 1404-06-01 (approximate; exact mapping depends on year specifics).

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Implementation Examples

Python (using a conceptual library):

from farsicalendar import FarsiCalendar fc = FarsiCalendar() jalali_date = fc.gregorian_to_jalali(2025, 3, 21) print(jalali_date)  # 1404-01-01 gregorian_date = fc.jalali_to_gregorian(1404, 1, 1) print(gregorian_date)  # 2025-03-21 

JavaScript (browser):

import { FarsiCalendar } from 'farsicalendar'; const fc = new FarsiCalendar(); console.log(fc.gregorianToJalali(2025, 3, 21)); // { year: 1404, month:1, day:1 } console.log(fc.jalaliToGregorian(1404,1,1));   // { year:2025, month:3, day:21 } 

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Handling Edge Cases and Historical Dates

• Pre-reform dates: The Persian calendar has undergone reforms; FarsiCalendar can optionally use historical conversion rules for dates before the modern reform.
• Leap-second and astronomical events: For millisecond-accurate timekeeping, pair the calendar with astronomical libraries.
• Different local practices: Some regions might observe different holiday rules; the calendar supports configurable holiday sets.

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Integration Examples

• Calendaring apps: show both Gregorian and Jalali dates side-by-side; set reminders on Jalali dates that translate to Gregorian alarms.
• Databases: store timestamps in ISO8601 (UTC) and present localized Jalali dates in the UI.
• APIs: endpoints like /convert?from=gregorian&to=jalali&date=2025-03-21 return JSON with converted date and metadata.

Sample API response:

{   "input": {"calendar":"gregorian","date":"2025-03-21"},   "output": {"calendar":"jalali","date":"1404-01-01"},   "timezone":"Asia/Tehran",   "notes":"Nowruz — Persian New Year" } 

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UI/UX Considerations

• Dual-calendar view: show Gregorian and Jalali grids; allow toggling primary display.
• Localization of numerals and text direction (RTL for Persian).
• Clear handling of ambiguous dates when users enter numeric dates (e.g., 03/04/1403).
• Performance: batch convert on the server for large datasets.

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Security, Testing, and Reliability

• Unit tests for conversion functions across a wide date range.
• Integration tests covering DST changes and timezone edge cases.
• Versioned API and predictable backward compatibility for developers.
• Use of authoritative astronomical libraries or ephemeris data when highest accuracy is required.

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Future Enhancements

• Add support for Afghan Dari labels and regional holiday variants.
• Voice and OCR input for handwritten Persian dates.
• Offline-capable mobile widgets with local holiday packs.
• Machine-learning suggestions for ambiguous date entries based on user locale.

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Conclusion

FarsiCalendar is a comprehensive solution for anyone needing reliable Persian (Jalali) date conversion, from developers integrating calendars into apps to users scheduling events aligned with Iranian cultural dates. With accurate algorithms, localization, holiday data, and developer-friendly APIs, FarsiCalendar bridges the gap between Gregorian and Persian timekeeping.