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How do I calculate time 4 hours ago in vbs or batch

I need to calculate the time 4 hours ago in a batch file or vbs and set it to a system variable.

Time now is 0900
fourHoursAgo = 0500

time now is 0200
fourHoursAgo = 2200
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1 Solution
Hello Brian,

The code below will popup a message with the time four hours ago in the format you are looking for.  Tell us a little more about the "system variable" part though... Do you mean an enviroment variable?

Nicolas Noakes

***** CODE BELOW ****

Function Pad(s,l,c)
's = String to pad (with prefix)
'l = Target length
'c = Character to pad with
Dim p
Dim i
  p = s
  Do While Len(p) < l
    p = c & p
  Pad = p
End Function

'You can use the following units:
'y = year
'm = month
'd = day
'h = hour
'n = minute
's = second

TgtTime = DateAdd("h", -4, Now())

MsgBox Pad(Hour(TgtTime), 2, "0") & Pad(Minute(TgtTime), 2, "0")
brian_appliedcpuAuthor Commented:
Yes, I apologize...

We have a script that calculates the hour as shown below but I need something that can subtract 4 hours from it and set it as an environment variable.

' from the  RunNow.vbs file in the question above, modified to display instead of setting:
Wscript.echo "set YY=" & Right("0" & Year(now()), 2)
Wscript.echo "set MM=" & Right("0" & Month(now()), 2)
Wscript.echo "set DD=" & Right("0" & Day(now()), 2)
Wscript.echo "set Hour=" & Right("0" & Hour(now()), 2)
Wscript.echo "set Min=" & Right("0" & Minute(now()), 2)
Wscript.echo "set Sec=" & Right("0" & Second(now()), 2)
Wscript.echo "set Now=%Hour%-%Min%-Hours"
'  continue the rest

To subtract 4 hours, set a variable (TgtTime in my first post) to the current time less 4 hours by using the vbscript DateAdd function as follows:

TgtTime = DateAdd("h", -4, now())   'This will set TgtTime to the current time less 4 hours

Now replace every instance of now() in your script with TgtTime to make it use the 4-hours-ago time.

I'll have to get back to you re the environment variable part...

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brian_appliedcpuAuthor Commented:
Not quite sure what I am doing wrong...

Wscript.Echo "set h= " & DatePart("h", now)
Wscript.echo "set TgtTime=" & DateAdd("h", -4, now())

Wscript.echo "set HSub4=" & Right("0" & Hour(TgtTime), 2)
Wscript.echo "set MSub4=" & Right("0" & Minute(TgtTime), 2)
Wscript.echo "set SSub4=" & Right("0" & Second(TgtTime), 2)

Wscript.Echo "set TgtHour= " & DatePart("hour", TgtTime)
Wscript.echo "set TgtHour=%TgtHour%"

Here is the output  ALL 00   ?????

F:\bin>set h= 13

F:\bin>set TgtTime=10/26/2006 9:20:33 AM

F:\bin>set HSub4=00

F:\bin>set MSub4=00

F:\bin>set SSub4=00
TgtTime=DateAdd("h",-4, TimeNow)

Wscript.Echo "set h= " & DatePart("h", TimeNow)
Wscript.echo "set TgtTime=" & TgtTime
Wscript.echo "set HSub4=" & Right("0" & DatePart("h",TgtTime), 2)
Wscript.echo "set MSub4=" & Right("0" & DatePart("m",TgtTime), 2)
Wscript.echo "set SSub4=" & Right("0" & DatePart("s",TgtTime), 2)

Wscript.Echo "set TgtHour= " & DatePart("h", TgtTime)
I posted the working version above.  What you were doing wrong was trying to use TgtTime but TgtTime was never set "in VBS/WSH".  

The following line would set a variable in the context of a batch file but not for VBS/WSH.
Wscript.echo "set TgtTime=" & DateAdd("h", -4, now())
brian_appliedcpuAuthor Commented:

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