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@StartAutomating
Last active March 13, 2026 20:31
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Gist gotta calculate Friday the 13th
function Get-Friday13th {
<#
.SYNOPSIS
Get Friday the 13th
.DESCRIPTION
Get the next N Friday the 13ths
.EXAMPLE
Get-Friday13th
#>
[Alias('Friday13th', 'Friday13', 'F13')]
param(
# The number of Friday the 13ths to find (by default, 13)
[ValidateRange(1,1kb)]
[Alias('Number')]
[int]
$N = 13,
# The starting date (by default, today)
[DateTime]
$Date = [DateTime]::Now.Date
)
$Day = $Date.Date
$FridayThe13th = @()
do {
# Because 5 and 13 are both prime
# Any .DayOfWeek * .Day will be 65
if ($day.DayOfWeek * $day.Day -eq 65) {
$FridayThe13th += $day
}
$day = $day.AddDays(1)
} while ($FridayThe13th.Count -lt $n)
$FridayThe13th
}
Get-Friday13th
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