RESTORE DATABASE successfully processed 15025885 pages in 3372.932 seconds (34.803 MB/sec).
That is a lot of seconds, but I was asked by management about the restore time. Just giving a couple of thousands of seconds was just not good enough.
But PowerShell came to the rescue with the CmdLet New–TimeSpan:
(New-TimeSpan -Seconds 3372.932).ToString()
that gives
00:56:13
The format is hh:mm:ss given by the ToString() method to the .NET TimeSpan structure.
As the CmdLet is based on the .NET TimeSpan structure, and PowerShell is integrated with .NET, it is also possible to use the static method FromSeconds() exposed by the structure:
[System.TimeSpan]::FromSeconds(3372.932).ToString()
The result is exactly the same — as expected.