ConvertTo-Approximation

function ConvertTo-Approximation {
    #.Synopsis
    #  Calculates a relative text version of a duration
    #.Description
    #  Generates a string approximation of a timespan, like "x minutes" or "x days." Note this method does not add "about" to the front, nor "ago" to the end unless you pass them in.
    #.Parameter Span
    #  A TimeSpan to convert to a string
    #.Parameter Before
    #  A DateTime representing the start of a timespan.
    #.Parameter After
    #  A DateTime representing the end of a timespan.
    #.Parameter Prefix
    #  The prefix string, pass "about" to render: "about 4 minutes"
    #.Parameter Postfix
    #  The postfix string, like "ago" to render: "about 4 minutes ago"
    [CmdletBinding(DefaultParameterSetName = "TwoDates")]
    PARAM (
        [Parameter(ParameterSetName = "TimeSpan", Mandatory, Position = 0)][TimeSpan]$TimeSpan,
        [Parameter(ParameterSetName = "TwoDates", Mandatory, ValueFromPipeline)][Alias("DateCreated")][DateTime]$StartTime,
        [Parameter(ParameterSetName = "TwoDates", Mandatory, Position = 0)][DateTime]$EndTime,
        [Parameter(Position = 1)][String]$Prefix = "",
        [Parameter(Position = 2)][String]$Postfix = "",
        [Parameter(Position = 3)][ValidateCount(6, 6)][String[]]$Units = @('seconds', 'a minute', 'minutes', 'an hour', 'hours', 'days')
    )
    PROCESS {
        if ($PSCmdlet.ParameterSetName -eq "TwoDates") {
            $TimeSpan = $EndTime - $StartTime
        }
        "$Prefix $($TimeSpan.Approximate($Units)) $Postfix ".Trim()
    }
}