Private/ConvertTo-UnixTime.ps1

Function ConvertTo-UnixTime {
    <#
.SYNOPSIS
Returns UnixTime of a given date.

.DESCRIPTION
Returns UnixTime as a whole number.

.PARAMETER Date
A DateTime object to return the UnixTime of.

.EXAMPLE
Get-Date | ConvertTo-UnixTime

#>

    [CmdletBinding()]
    [OutputType('System.Integer')]
    Param(
        [Parameter(
            Mandatory = $true,
            ValueFromPipeline = $true
        )]
        [DateTime]$Date,

        [Parameter(
            Mandatory = $false,
            ValueFromPipeline = $false
        )]
        [switch]$Milliseconds
    )
    begin {
        $currentCulture = [System.Threading.Thread]::CurrentThread.CurrentCulture
    }
    process {
        [System.Threading.Thread]::CurrentThread.CurrentCulture = 'en-US'

        $UnixTime = [math]::Round($(Get-Date $Date.ToUniversalTime() -UFormat %s))

        If ($Milliseconds) {
            $UnixTime = $UnixTime * 1000
        }

        $UnixTime
    }
    end {
        [System.Threading.Thread]::CurrentThread.CurrentCulture = $currentCulture
    }
}