Time Zone issue

We have set EST as our time in the system & its the default time zone for users. But when checking there is 1 hour difference in the time . What could be the cause.

We have tried changing the timezone using STZAC & still the same.

Screen Info

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Previous logon 26.03.2010 ; 02:00:19

Logon 02:59:04

System time 03:19:14 <====== System time in EST

Time zone EST 02:19:14

Please suggest..