Daylight Savings Time is Coming! Is Your SIM/DPM Implementation Ready?

by Moderator Moderator on ‎03-09-2012 12:44 PM - last edited on ‎07-23-2012 02:50 PM by Administrator Administrator (19,639 Views)

This weekend the US will be switching to Daylight Savings Time. While this should have little impact, some merchants using SIM or DPM may experience errors related to their transaction fingerprint (RRCs 97, 98, 99 or 103.)


The transaction fingerprint depends on a timestamp expressed in POSIX Time, sometimes called UNIX Epoch Time. Simply put, it is the number of seconds since January 1, 1970, at Midnight UTC. If you take the current time in the server’s time zone and convert that to UTC, and then use that to calculate POSIX Time, that may introduce the risk of the time being miscalculated when the server switches from Standard Time to Daylight Savings Time. This will cause transaction fingerprints to fail.


To avoid this, we recommend the following:


  • Take care to use whatever options are available in your scripting language of choice to use POSIX time automatically, instead of trying to convert from local time to POSIX time. Most scripting languages support POSIX timestamps.
  • Make sure the Web server is using UTC, not local time.
  • The operating systems on Web servers should be kept up to date. Since Daylight Savings Time is defined by law and is subject to change, servers may need to be updated to reflect changes.
  • Where possible, Web servers should use the Network Time Protocol (NTP) to keep their clocks synchronized.