Powershell: Comparing Dates

Powershell: Comparing Dates

I am querying a data source for dates. Depending on the item I am searching for, it may have more than date associated with it.

get-date ($Output | Select-Object -ExpandProperty "Date")

An example of the output looks like:

Monday, April 08, 2013 12:00:00 AM
Friday, April 08, 2011 12:00:00 AM

I would like to compare these dates and return which one is set further out into the future.

4 Answers

As Get-Date returns a DateTime object you are able to compare them directly. An example:

(get-date 2010-01-02) -lt (get-date 2010-01-01)

will return false.

0

I wanted to show how powerful it can be aside from just checking "-lt".

Example: I used it to calculate time differences take from Windows event view Application log:

Get the difference between the two date times:

PS> $Obj = ((get-date "10/22/2020 12:51:1") - (get-date "10/22/2020 12:20:1 "))

Object created:

PS> $Obj


Days              : 0
Hours             : 0
Minutes           : 31
Seconds           : 0
Milliseconds      : 0
Ticks             : 18600000000
TotalDays         : 0.0215277777777778
TotalHours        : 0.516666666666667
TotalMinutes      : 31
TotalSeconds      : 1860
TotalMilliseconds : 1860000

Access an item directly:

PS> $Obj.Minutes
31
1

Late but more complete answer in point of getting the most advanced date from $Output

## Q:\test\2011\02\SO_5097125.ps1
## simulate object input with a here string 
$Output = @"
"Date"
"Monday, April 08, 2013 12:00:00 AM"
"Friday, April 08, 2011 12:00:00 AM"
"@ -split '\r?\n' | ConvertFrom-Csv

## use Get-Date and calculated property in a pipeline
$Output | Select-Object @{n='Date';e={Get-Date $_.Date}} |
    Sort-Object Date | Select-Object -Last 1 -Expand Date

## use Get-Date in a ForEach-Object
$Output.Date | ForEach-Object{Get-Date $_} |
    Sort-Object | Select-Object -Last 1

## use [datetime]::ParseExact
## the following will only work if your locale is English for day, month day abbrev.
$Output.Date | ForEach-Object{
    [datetime]::ParseExact($_,'dddd, MMMM dd, yyyy hh:mm:ss tt',$Null)
} | Sort-Object | Select-Object -Last 1

## for non English locales
$Output.Date | ForEach-Object{
    [datetime]::ParseExact($_,'dddd, MMMM dd, yyyy hh:mm:ss tt',[cultureinfo]::InvariantCulture)
} | Sort-Object | Select-Object -Last 1

## in case the day month abbreviations are in other languages, here German
## simulate object input with a here string 
$Output = @"
"Date"
"Montag, April 08, 2013 00:00:00"
"Freidag, April 08, 2011 00:00:00"
"@ -split '\r?\n' | ConvertFrom-Csv
$CIDE = New-Object System.Globalization.CultureInfo("de-DE")
$Output.Date | ForEach-Object{
    [datetime]::ParseExact($_,'dddd, MMMM dd, yyyy HH:mm:ss',$CIDE)
} | Sort-Object | Select-Object -Last 1
1

Considering you want to include time also, I have included sample. I am putting datetime in the ISO8601, so it works in locale agnostic manner.

Monday, April 08, 2013 12:00:00 AM Friday, April 08, 2011 12:00:00 AM

(Get-date "2013-04-08T00:00:00") -lt (Get-Date "2011-04-08T00:00:00")

False

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Marcus Vance
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Marcus Vance

Marcus Vance is a cybersecurity auditor and technology writer dedicated to educating the public about online safety, data privacy regulations, enterprise security, and emerging cyber threats.