Is there a standard DateTime string representation that is valid as a Windows file name and can be parsed using DateTime.Parse?

Question

As part of a simple backup process, I would like to save files with the name indicating the date and time of the backup. Right now I am using yyyyMMddTHHmmss, i.e. "20100601T115720". I would like to be able to parse those dates back to allow clean up of files older than a certain date. (The backup date time is not necessary the same as the file created date.) This ultimately runs in Powershell, using a line something like the following:

Get-ChildItem $backupDirectory -filter *.bak | where { [System.DateTime]::ParseExact([System.IO.Path]::GetFileNameWithoutExtension($_), "yyyyMMddTHHmmss", [System.Globalization.CultureInfo]::InvariantCulture) -lt $oldestDate }

Note that I am currently using the DateTime.ParseExact method. This works great, and so I guess my question is more academic, but I'm wondering if there a "standard" Windows file name format that:

• Includes both date and time information AND
• Can be parsed using the standard DateTime.Parse

Answer 1

This is no "standard" filename format.

I usually use yyyy-MM-dd, HH-mm-ss, which is a lot more readable than a blob of numbers.

Answer 2

There isn't a standard filename format that I've found, either, but this trick tends to work well for making PowerShell output a localized readable date/time (i.e. February 2nd, 2010 8:15:14 AM):

(Get-Date | Out-String).Trim().Replace(":", "-")

Piping Get-Date to Out-String uses the default formatter (in this case, the time in the current locale) to make the date a readable string. Trim() removes the extra newlines from both ends. Since the only illegal character in the time strings of of the locales I am aware of is ':', I simply replace ':' with '-'

It's most definately a notch slower than using .NET's string formatting. If you want to use the same trick without using cmdlets, you can write it this way:

$date = [DateTime]::Now
($date.ToLongDateString() + " " + $date.ToLongTimeString()).Replace(":",'-')

Hope this helps