jalcal (version 0.3.0)

greg2jal: Convert Gregorian Dates to Jalaali (Persian) Calendar

Description

This function converts a vector of Gregorian dates (in `Date` format) to their corresponding Jalaali (Persian) calendar dates. It correctly handles leap years and determines the exact Jalaali year, month, and day for each input date.

Usage

greg2jal(dates)

Value

A data frame with three columns:

Year

The corresponding Jalaali year.

Month

The corresponding Jalaali month.

Day

The corresponding Jalaali day.

If a single date is provided, a numeric vector of length 3 (Year, Month, Day) is returned.

Arguments

dates

A vector of class `Date` representing the Gregorian dates to be converted.

Details

The Jalaali calendar is a solar calendar with an irregular leap year pattern. This function follows an algorithm based on equinox calculations to accurately determine the Jalaali date for each given Gregorian date.

**Conversion Process:** - The function first ensures that the input is of class `Date`. - It estimates the Jalaali year by subtracting 621 from the Gregorian year. - Leap year information for relevant Jalaali years is obtained using `jalLeap`. - The function then determines the first day of the Jalaali year in the Gregorian calendar. - Using cumulative day counts, it calculates the Jalaali month and day. - If the input date falls before the start of the Jalaali year (before March 21), an adjustment is made to account for the previous year.

The function efficiently handles both single and multiple date inputs, returning either a numeric vector (for a single date) or a well-structured data frame.

See Also

- jalLeap for computing leap year information. - jal2greg for converting Jalaali dates to Gregorian dates

Examples

# Convert a single Gregorian date to Jalaali
greg2jal(as.Date("2024-03-21"))

# Convert multiple dates
greg2jal(as.Date(c("2024-03-21", "2024-04-10", "2025-01-01")))