As the change for daylight saving is approaching, we would like to remind you that the hotfix with the most recent change for the “(UTC -4:00) Santiago” time zone covering changes on time for 2012 can be downloaded from KB2681116. If you already installed this hotfix, there is no action required as this hotfix already includes the change for DST to start September 1, 2012 at 23:59:59.999 and the clock to advance to 01:00:00.000 of September 2.
If by some reason you did not installed this hotfix for the past time change occurred on April, then you have to manually download the hotfix KB2681116 and install it before time change occur in order to allow your system have the accurate time. This hotfix will not be offered through Windows Update at this time, so please, be aware of this situation if you were expecting to receive it in this way. Sincerely we apologize for this inconvenience that could cause to you.