function Get-DateRange {
    param(
        [Parameter(Mandatory = $true)]
        [ValidateNotNull()]
        [datetime] $StartDate,
        $EndDate,

        [timespan] $Duration,

        [ValidateNotNull()]
        [timespan] $Step = [timespan]::FromDays(1)
    )
    if ($Duration -ne $null -and $EndDate -ne $null) {
        throw 'Can not set both $Duration and $EndDate'
    }
    if ($EndDate -ne $null) {
        $EndDate = [datetime]$EndDate
    }
    if ($Duration -ne $null) {
        $EndDate = $StartDate + $Duration
    }
    if ($EndDate -eq $null) {
        throw 'Must set $Duration or $EndDate'
    }
    if ($EndDate -le $StartDate) {
        throw '$EndDate must be greater than $StartDate'
    }

    $d = $StartDate
    while ($d -lt $EndDate) {
        $d
        $d = $d + $Step
    }
}