I think it depends on what you mean by EST - if you mean East Coast US, then in general, that is 5 hours behind UTC (but not accounting for daylight saving), which should give you 04:00 EST. Try to avoid using abbreviations where possible, as they are ambiguous, e.g. EST is the abbreviation for both America/Detroit and Australia/Sydney. Using NSTimeZone initWithName will give more precise results.
The Chronos Time Zone Repository provides a nicely readable XML timezone database that really helps in understanding how time zones work (it's all rather messy and changeable).
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