🚀 [Feature]: Add Get-CurrentDateTime function (#14)

The module now includes a new `Get-CurrentDateTime` function that
provides flexible date and time formatting options. You can retrieve the
current date/time in multiple preset formats or specify your own custom
format string, making it easier to generate timestamps for logging, file
naming, or display purposes.

- Fixes #15

## New function: Get-CurrentDateTime

A new public function `Get-CurrentDateTime` is available with the
following format options:

| Format | Description | Example Output |
|--------|-------------|----------------|
| `Default` | Standard timestamp format | `2026-01-20 14:30:45` |
| `Short` | Locale-specific short date | `1/20/2026` |
| `Long` | Locale-specific long date | `Monday, January 20, 2026` |
| `ISO8601` | ISO 8601 format with timezone |
`2026-01-20T14:30:45.1234567+01:00` |
| `Custom` | User-defined format string | Depends on `-CustomFormat`
parameter |

### Usage examples

```powershell
# Get current date/time in default format
Get-CurrentDateTime
# Returns: 2026-01-20 14:30:45

# Get ISO 8601 formatted timestamp
Get-CurrentDateTime -Format 'ISO8601'
# Returns: 2026-01-20T14:30:45.1234567+01:00

# Use a custom format
Get-CurrentDateTime -Format 'Custom' -CustomFormat 'dddd, MMMM dd, yyyy'
# Returns: Monday, January 20, 2026
```

## Tests included

Comprehensive Pester tests are included covering all format options to
ensure reliable functionality.

Author: MariusStorhaug

src/functions/public/Get-CurrentDateTime.ps1

@@ -0,0 +1,60 @@
+function Get-CurrentDateTime {
+    <#
+        .SYNOPSIS
+        Returns the current date and time in a specified format.
+
+        .DESCRIPTION
+        Returns the current date and time formatted according to the specified format string.
+        Supports common format presets or custom format strings.
+
+        .EXAMPLE
+        Get-CurrentDateTime
+
+        Returns the current date and time in the default format (yyyy-MM-dd HH:mm:ss).
+
+        .EXAMPLE
+        Get-CurrentDateTime -Format 'Short'
+
+        Returns the current date in short date format.
+
+        .EXAMPLE
+        Get-CurrentDateTime -Format 'Custom' -CustomFormat 'dddd, MMMM dd, yyyy'
+
+        Returns the current date in a custom format like "Monday, January 20, 2026".
+
+        .LINK
+        https://MariusStorhaug.github.io/MariusTestModule/Functions/Get-CurrentDateTime/
+    #>
+    [OutputType([string])]
+    [CmdletBinding()]
+    param (
+        # The format preset to use for the date and time output.
+        [Parameter()]
+        [ValidateSet('Default', 'Short', 'Long', 'ISO8601', 'Custom')]
+        [string] $Format = 'Default',
+
+        # Custom format string when Format is set to 'Custom'.
+        [Parameter()]
+        [string] $CustomFormat = 'yyyy-MM-dd HH:mm:ss'
+    )
+
+    $currentDateTime = Get-Date
+
+    switch ($Format) {
+        'Default' {
+            $currentDateTime.ToString('yyyy-MM-dd HH:mm:ss')
+        }
+        'Short' {
+            $currentDateTime.ToShortDateString()
+        }
+        'Long' {
+            $currentDateTime.ToLongDateString()
+        }
+        'ISO8601' {
+            $currentDateTime.ToString('o')
+        }
+        'Custom' {
+            $currentDateTime.ToString($CustomFormat)
+        }
+    }
+}

tests/PSModuleTest.Tests.ps1

@@ -21,4 +21,29 @@ Describe 'Module' {
     It 'Function: Get-Greeting - Evening' {
         Get-Greeting -TimeOfDay 'Evening' | Should -Be 'Good Evening!'
     }
+
+    It 'Function: Get-CurrentDateTime - Default format' {
+        $result = Get-CurrentDateTime
+        $result | Should -Match '^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}$'
+    }
+
+    It 'Function: Get-CurrentDateTime - ISO8601 format' {
+        $result = Get-CurrentDateTime -Format 'ISO8601'
+        $result | Should -Match '^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}'
+    }
+
+    It 'Function: Get-CurrentDateTime - Custom format' {
+        $result = Get-CurrentDateTime -Format 'Custom' -CustomFormat 'yyyy'
+        $result | Should -Be (Get-Date).ToString('yyyy')
+    }
+
+    It 'Function: Get-CurrentDateTime - Short format' {
+        $result = Get-CurrentDateTime -Format 'Short'
+        $result | Should -Not -BeNullOrEmpty
+    }
+
+    It 'Function: Get-CurrentDateTime - Long format' {
+        $result = Get-CurrentDateTime -Format 'Long'
+        $result | Should -Not -BeNullOrEmpty
+    }
 }