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UGU: Unix Guru Universe - Unix Tip #4460- May 28, 2025
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 Unix Tip #4460- May 28, 2025
 
SOLARIS CHANGING SEASONS  
  
During a session, sometimes  
we have a need to change the  
system time for our session  
only.  We have used it to  
simulate time based testing.  
  
export TZ=ESThhEDT  
  
The EST set your time to Eastern  
Standard Time and EDT is Eastern  
Daylight Time.  
  
hh is the number of hours you  
wish to change.  
  
Example:  Currently the system  
date is  Tue Jun 19 13:38:03 EDT 2001  
  
and you wish to set it to  
yesterday at the same time.  
You would substitute a positive  
29 for hh.  
  
export TZ=EST29EDT  
  
Now the shell time is:  
Mon Jun 18 13:38:50 EDT 2001  
  
WHY 29 and not 24?  The main  
UNIX clock is set from GMT not  
EST therefore you have to add  
5 hours to your backward  
calculations to get the same  
exact time since EST is  
GMT - 5 hours.  
  
Use negitive numbers to set  
the clock into the future.  
  
Also if you need to set the  
minutes and seconds  it is  
hh:mm:ss.  These are all the  
number of hours, minutes and  
seconds from GMT that you wish  
to set.  
  
This is for Solaris 2.6, your  
mileage may vary.  
  
 NOTE: All tips provided are USE AT YOUR OWN RISK. Tips are submitted
by various unix admins around the globe. UGU suggest you read and
test each tip in a non-volitile environment before placing into
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