The function below will calculate the date of Easter Sunday.
Function Get-DateOfEaster {
param (
[int]$Year,
[int]$GregorianStart = 1752
)
# Reads a Year and returns the date of Easter Sunday.
# For Easter dates prior to 1926 the start of the Gregorian calendar needs to be considered.
# Different countries adopted the Gregorian calendar on different dates.
# France, Spain, Portugal = 1582
# Netherlands = 1583
# Switzerland = 1584
# UK + colonies = 1752
# Turkey = 1926
# Setting $GregorianStart > $Year, will return Easter on the Julian calendar.
[int]$GoldenNo = $Year % 19 #modulus
If ($Year -gt $GregorianStart) {
[int]$Century = [math]::floor($Year / 100)
[int]$intK = [math]::floor(($Century - 17) / 25)
[int]$intI = $Century - [math]::floor(($Century / 4))
[int]$intI = $intI - [math]::floor((($Century - $intK) / 3)) + 19 * $GoldenNo + 15
[int]$intI = $intI % 30
[int]$intN1 = $intI - [math]::floor(($intI / 28))
[int]$intN21 = [math]::floor(($intI / 28))
[int]$intN22 = [math]::floor((29 / ($intI + 1)))
[int]$intN23 = [math]::floor(((21 - $GoldenNo) / 11))
[int]$intI = $intN1 * (1 - $intN21 * $intN22 * $intN23)
[int]$intJ = $Year + [math]::floor(($Year / 4)) + $intI
[int]$intJ = $intJ + 2 - $Century + [math]::floor(($Century / 4))
[int]$intJ = $intJ % 7
$Cal = 'Gregorian'
} Else {
[int]$intI = ((19 * $GoldenNo) + 15) % 30
[int]$intJ = ($Year + [math]::floor(($Year / 4)) + $intI) % 7
$Cal = 'Julian'
}
[int]$intL = $intI - $intJ
[int]$Month = 3 + [math]::floor((($intL + 40) / 44))
[int]$Day = $intL + 28 - 31 * [math]::floor(($Month / 4))
"$Year-0$Month-$Day ($Cal)"
$DateTime = New-Object DateTime $Year, $Month, ($Day), 0, 0, 0, ([DateTimeKind]::Utc)
Return $DateTime
}
" Examples:"
$Easter = Get-DateOfEaster 2025
"$Easter"
$Easter = Get-DateOfEaster 1590 1752
"$Easter"
“If you are lucky enough to have lived in Paris as a young man, then wherever you go for the rest of your life, it stays with you, for Paris is a moveable feast” ~ Ernest Hemingway
Get-BankHolidaysUK - Retrieve UK Bank Holidays from a web service.
Adoption of the Gregorian calendar - Wikipedia.