Boostgregoriandate day number returns julian date

When working with dates in Julia, there are several ways to convert a Gregorian date to a Julian date. In this article, we will explore three different approaches to solve the given problem.

Approach 1: Using the Dates package

The Dates package in Julia provides a convenient way to work with dates and perform various operations. To convert a Gregorian date to a Julian date using this package, we can use the `Dates.datetime2julian()` function.

using Dates

function boostgregoriandate(day_number)
    gregorian_date = Dates.Date(day_number)
    julian_date = Dates.datetime2julian(Dates.DateTime(gregorian_date))
    return julian_date
end

In this approach, we first create a `Date` object from the given day number. Then, we convert it to a `DateTime` object and pass it to the `datetime2julian()` function to obtain the Julian date.

Approach 2: Using the Dates package with custom calculations

If you prefer to avoid using the `datetime2julian()` function, you can manually calculate the Julian date using the formulas provided by the National Aeronautics and Space Administration (NASA).

using Dates

function boostgregoriandate(day_number)
    gregorian_date = Dates.Date(day_number)
    year = Dates.year(gregorian_date)
    month = Dates.month(gregorian_date)
    day = Dates.day(gregorian_date)

    a = div((14 - month), 12)
    y = year + 4800 - a
    m = month + 12 * a - 3

    julian_date = day + div((153 * m + 2), 5) + 365 * y + div(y, 4) - div(y, 100) + div(y, 400) - 32045

    return julian_date
end

In this approach, we extract the year, month, and day components from the given day number. Then, we apply the NASA-provided formulas to calculate the Julian date.

Approach 3: Using the Dates package with the `julian2datetime()` function

Another way to convert a Gregorian date to a Julian date is by using the `julian2datetime()` function from the Dates package. This function takes a Julian date as input and returns a DateTime object.

using Dates

function boostgregoriandate(day_number)
    gregorian_date = Dates.Date(day_number)
    julian_date = Dates.datetime2julian(Dates.DateTime(gregorian_date))
    julian_datetime = Dates.julian2datetime(julian_date)
    return julian_datetime
end

In this approach, we first convert the Gregorian date to a Julian date using the `datetime2julian()` function. Then, we pass the Julian date to the `julian2datetime()` function to obtain a DateTime object representing the Julian date.

After analyzing the three approaches, it is evident that Approach 1, which uses the `datetime2julian()` function, is the most straightforward and concise solution. It leverages the built-in functionality of the Dates package and avoids the need for manual calculations. Therefore, Approach 1 is the recommended option for converting a Gregorian date to a Julian date in Julia.