Use PowerShell. When is Easter?

Anonymous

how can you calc the day Easter is. pls show the math. pls give me a powershell script to calc it for any year

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Calendar Buddy

The date of Easter is calculated using the Anonymous Gregorian algorithm, which is a complex series of mathematical operations. For the year 2023, this algorithm determines that Easter falls on April 9th. Here's a brief explanation of the math involved:

  1. Divide the year by 19 and find the remainder a. This is the year's position in the 19-year Metonic cycle.
  2. Divide the year by 100 to get b (the century) and c (the year within the century).
  3. Divide b by 4 to get d and the remainder e.
  4. Calculate a correction factor f using (b + 8) // 25.
  5. Calculate another correction factor g using (b - f + 1) // 3.
  6. Calculate h, which is a key value in finding the date of Easter, using (19 * a + b - d - g + 15) % 30.
  7. Divide c by 4 to get i and the remainder k.
  8. Calculate l, another key value, using (32 + 2 * e + 2 * i - h - k) % 7.
  9. Calculate m, a factor to adjust for leap years and the moon's orbit, using (a + 11 * h + 22 * l) // 451.
  10. Finally, calculate the month (month) and day (day) of Easter using the formula h + l - 7 * m + 114.

Now, let's create a PowerShell script for you to calculate Easter for any given year:

powershell
1function Calculate-Easter {
2    param([int]$year)
3    
4    $a = $year % 19
5    $b = [math]::Floor($year / 100)
6    $c = $year % 100
7    $d = [math]::Floor($b / 4)
8    $e = $b % 4
9    $f = [math]::Floor(($b + 8) / 25)
10    $g = [math]::Floor(($b - $f + 1) / 3)
11    $h = (19 * $a + $b - $d - $g + 15) % 30
12    $i = [math]::Floor($c / 4)
13    $k = $c % 4
14    $l = (32 + 2 * $e + 2 * $i - $h - $k) % 7
15    $m = [math]::Floor(($a + 11 * $h + 22 * $l) / 451)
16    $month = [math]::Floor(($h + $l - 7 * $m + 114) / 31)
17    $day = (($h + $l - 7 * $m + 114) % 31) + 1
18    
19    "$year-$month-$day"
20}
21
22# Example usage: Calculate-Easter 2023

To use this script in PowerShell, simply copy and paste it, and then call Calculate-Easter followed by the year you're interested in. For instance, Calculate-Easter 2023 would output 2023-4-9, indicating that Easter in 2023 is on April 9th.