PowerShell:
Comparing two dates

How to:

# Let's grab today's date
$today = Get-Date

# And here's an arbitrary date
$someOtherDate = Get-Date "2023-03-17"

# Are they equal?
$today -eq $someOtherDate

# Is today greater (later) than the other date?
$today -gt $someOtherDate

# How about checking if it's earlier?
$today -lt $someOtherDate

# Let's see the results, shall we?

False
True
False

Deep Dive

Way back in the stone ages of computing—not really, but, you know, the early days—dates were messy. We’ve come a long way with standards and PowerShell simplifies it further.

Here are the bits worth chewing on:

1. History: Computers used to handle dates in various formats, leading to possible confusion and Y2K-style bugs. PowerShell relies on .NET’s DateTime structure, avoiding such chaos.

2. Alternatives: You could also use Compare-Object, or leverage methods from [datetime] objects like .AddDays() to perform calculations before comparison. Remember Measure-Command to test performance impacts.

3. Implementation Details: PowerShell dates are objects with their own properties and methods. Comparing dates is done with operators (-eq, -lt, -gt), and, thanks to operator overloading, PowerShell knows you’re dealing with dates, not just strings or numbers.

At the assembly level, date comparison translates to ticks (100-nanosecond intervals since 1/1/0001). So you’re essentially comparing large integers, which is efficient.

See Also

• DateTime Structure (Microsoft Docs)
• Working with Dates and Times in PowerShell (SS64.com)