How to split a date range into monthly subranges in PowerShell? - powershell

Question

In Powershell, assuming:
$rangeFrom = "2020-03-01"
$rangeTo = "2020-05-13"
How could I obtain:
$monthRange[0] = "2020-03-01","2020-03-31"
$monthRange[1] = "2020-04-01","2020-04-30"
$monthRange[2] = "2020-05-01","2020-05-13"
Dates will be used in a loop as strings (from/to) on commands that do not support more than one month in range, such as:
myCommand -From $rangeFrom -To $rangeTo # keep this in one month range

Answer 1

By using DateTime objects you can solve the most trouble, like calculating the last day of a month or iterating over dates. You can use the following code to solve your problem:
$rangeFrom = "2019-12-15"
$rangeTo = "2020-05-13"
$monthRange = #()
$dateFrom = Get-Date $rangeFrom
$dateTo = Get-Date $rangeTo
$dateCur = Get-Date $dateFrom -Day 1
while ($dateCur -lt $dateTo) {
if (($dateCur.Year -eq $dateFrom.Year) -and ($dateCur.Month -eq $dateFrom.Month)) {
$dateBegin = $dateFrom # First month exception
} else {
$dateBegin = $dateCur
}
if (($dateCur.Year -eq $dateTo.Year) -and ($dateCur.Month -eq $dateTo.Month)) {
$dateEnd = $dateTo # Last month exception
} else {
$dateEnd = $dateCur.AddMonths(1).AddDays(-1)
}
$monthRange += [Tuple]::Create($dateBegin.toString('yyyy-MM-dd'), $dateEnd.toString('yyyy-MM-dd'))
$dateCur = $dateCur.AddMonths(1)
}
$monthRange
Output:
Item1 Item2 Length
----- ----- ------
2019-12-15 2019-12-31 2
2020-01-01 2020-01-31 2
2020-02-01 2020-02-29 2
2020-03-01 2020-03-31 2
2020-04-01 2020-04-30 2
2020-05-01 2020-05-13 2
You can access individual elements like this:
$monthRange[2].Item2
Output:
2020-02-29