Hi Julio,
It seems that there have been different problems with different phone types/models.
For 7940/7960;
This problem for 7940's and 7960's was discovered Sunday AM. Here is a good description of the fix from Mahesh@Cisco (I guess this was part of the OS Upgrade not mentioned in the Manual Workaround);
If the issue is only with 7940/60 phones, then we have seen a lot of similar cases today and are working to get a permanent fix to the issue. However as a workaround, you could resolve it by going into the Start >> Programs >> Microsoft SQL Server >> Enterprise Manager >> CCM database >> Table >> "TypeTimeZone" >> Right Click Open Table >> Return All Rows and manually set the "stddate" and "dstdate" to "0/11/0/1,2:0:0:0" and "0/3/0/2,2:0:0:0" respectively for each US timezone.
CM Service needs to be restarted.
From this long detailed thread;
http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Unified%20Communications%20and%20Video&topic=IP%20Telephony&CommCmd=MB?cmd=display_location&location=.1dddd0fe/40
For Java based phones;
Java based phones (7906G,7911G,7941G,7961G,7970 or 7971)need a firmware upgrade to 8.2.1.
Look at(Step 2).
To obtain the complete Daylight Savings Time (DST) Update for the Operating System, Unified CallManager Cluster, and the 7906, 7911, 7921, 7941, 7961, 7970, 7971 IP phone models, you must perform the following steps in order:
1. Apply the Operating System (OS) 2000.4.2sr14, 2000.4.3aSR7, 2000.4.4sr2 or HIGHER, found here:
http://www.cisco.com/cgi-bin/tablebuild.pl/cmva-3des
2. Apply either the 8.2.1 stand-alone phone load or the device pack for this release:
8.2.1 Stand-alone phone load found here:
http://www.cisco.com/cgi-bin/tablebuild.pl/ip-7900ser
Device Pack for Unified CallManager 4.1(3), found here:
http://www.cisco.com/cgi-bin/tablebuild.pl/callmgr-41
3. Apply the Unified CallManager Update, found here:
http://www.cisco.com/cgi-bin/tablebuild.pl/callmgr-41
From this doc;
http://ftp-sj.cisco.com/cisco/crypto/3DES/voice/callmgr/4.1/ciscocm.4-1-3-2007-DST-Update.1-0-1-readme.htm
Hope this helps!
Rob