This post will show two ways to determine the time span between two datetimes.

Earlier this year we performed a data migration to our data center. One of the Assistant Directors sent me an instant message first thing on a Monday morning to ask if the migration was complete. I had read that it completed earlier that morning and so I replied with the time at which it ended. The second question was how long the entire data migration took. I knew it started at 11 a.m. on Friday and that it completed at 7:21 a.m. on Monday. I could have done this in my head (11 a.m. Friday to 11 a.m. Monday equals 3 days, minus 4 hours, etc.) but I trust Windows PowerShell with dates, times, and time spans more than I do myself.

The first thing I did was assign a variable, $StateDate, with the date and time when the data migration started. After testing to see it held the proper date and time, I created a second variable, $EndDate, and assigned it the date and time when the data migration ended. I also checked that it stored the correct date and time before moving on.

PS C:\> $StartDate = Get-Date '5/9/2014 11:00:00 AM'
PS C:\> $StartDate

Friday, May 09, 2014 11:00:00 AM

PS C:\> $EndDate = Get-Date '5/12/2014 07:21:00 AM'
PS C:\> $EndDate

Monday, May 12, 2014 7:21:00 AM

I was aware of the New-TimeSpan cmdlet, which we’ll use below, but I wondered if I could simply subtract the start date (the smaller date and time) from the end date (the larger date and time). I tried and it worked! Two days, 20 hours, 21 minutes.

PS C:\> $EndDate - $StartDate

Days              : 2
Hours             : 20
Minutes           : 21
Seconds           : 0
Milliseconds      : 0
Ticks             : 2460600000000
TotalDays         : 2.84791666666667
TotalHours        : 68.35
TotalMinutes      : 4101
TotalSeconds      : 246060
TotalMilliseconds : 246060000

Here’s an example of using the New-TimeSpan cmdlet. Using this cmdlet may be easier, as to not confuse which date to subtract from which.

PS C:\> New-TimeSpan -Start $StartDate -End $EndDate

Days              : 2
Hours             : 20
Minutes           : 21
Seconds           : 0
Milliseconds      : 0
Ticks             : 2460600000000
TotalDays         : 2.84791666666667
TotalHours        : 68.35
TotalMinutes      : 4101
TotalSeconds      : 246060
TotalMilliseconds : 246060000

I didn’t want anything more returned to me other than the days, hours, and minutes. I piped my results from the New-TimeSpan cmdlet to the Select-Object cmdlet and specified the properties I wanted returned. The output wasn’t great (see the final example on this page) and so I took those results and piped them to the Format-List cmdlet.

PS C:\> New-TimeSpan -Start $StartDate -End $EndDate | Select-Object Days,Hours,Minutes | Format-List

Days    : 2
Hours   : 20
Minutes : 21

Here’s how I finished up. I created a new variable, $TimeSpan, and assigned it the results of the New-TimeSpan cmdlet piped the Select-Object cmdlet. Before going any further, I tested that the variable’s value was storing what I wanted. Once I was sure the  variable contained what I wanted, I modified it a bit and sent it to the clipboard so it could be easily pasted into my instant messenger program.

PS C:\> $TimeSpan = New-TimeSpan -Start $StartDate -End $EndDate | Select-Object Days,Hours,Minutes
PS C:\> $TimeSpan

                                   Days                                   Hours                                 Minutes
                                   ----                                   -----                                 -------
                                      2                                      20                                      21

PS C:\>"$($TimeSpan.Days) Days, $($TimeSpan.Hours) Hours, $($TimeSpan.Minutes) Minutes" | clip