Question: Can anybody tell about three things:

1. How to retrieve TimeZone from java.util.Date instance?
2. How to know whether Daylight savings is applicable?  
I suppose I can know it by doing timeZone.getDSTSavings, but problem I am facing is that even if I make my system's date as Feb 1 2012, still I am getting the value as positive (I guess 3600000)
3. How to convert EST time to EDT or vice versa?

Answer: 
> 
> How to retrieve TimeZone from java.util.Date instance?
> 
> 
> 

There's no such thing. A `Date` *just* represents a number of milliseconds since the Unix epoch, which was midnight on January 1st 1970 UTC. It's not associated with a particular calendar system or time zone. To put it another way, if a friend and I are on the phone together (with a zero latency ;) and I click my fingers, we would both agree on the `Date` at which that click too place - even if I'm using the Gregorian calendar and he's using the Julian calendar, and even if I'm in London and he's in New York. It's the same *instant in time*.

> 
> How to know whether Daylight savings is applicable?, I suppose I can know it by doing timeZone.getDSTSavings, but problem I am facing is that even if I make my system's date as Feb 1 2012, still I am getting the value as positive (I guess 3600000)
> 
> 
> 

Ideally, use [Joda Time](http://joda-time.sf.net) instead of `java.util.Date`/`Calendar`/`TimeZone`, but within `TimeZone` you can use [`TimeZone.getOffset(long)`](http://docs.oracle.com/javase/7/docs/api/java/util/TimeZone.html#getOffset%28long%29) to find the offset from UTC, or [`TimeZone.inDaylightTime(Date)`](http://docs.oracle.com/javase/7/docs/api/java/util/TimeZone.html#inDaylightTime%28java.util.Date%29) to just give you a yes/no answer.

> 
> How to convert EST time to EDT or vice versa?
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> 
> 

Usually that's an invalid question - because at any one instance in time, *either* EST *or* EDT applies. You normally convert from one *time zone* to another, and "EDT" and "EST" aren't different time zones - they're different offsets within the *same* time zone. The fact that you're asking for this suggests that you may be modelling your data incorrectly to start with (which is unfortunately easy to do with date/time values). Please give us more information and we may be able to help you more.
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> 1. How to retrieve TimeZone from java.util.Date instance?
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> 
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You can view the Time Zone of an instantiated Date object by viewing it in toString() format. Such as "Wed May 01 12:00:00 EDT 2013". 

> 
> How to know whether Daylight savings is applicable?, I suppose I can know it by doing timeZone.getDSTSavings, but problem I am facing is that even if I make my system's date as Feb 1 2012, still I am getting the value as positive (I guess 3600000) 3. How to convert EST time to EDT or vice versa? This is critical question I have
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> 
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The Date object will account for the EDT/EST automatically. For instance, if you have an instantiated Date object for November 28, then the toString() will include EST rather than EDT. 

The problem I originally ran into was that I was trying to use EST for a calendar date where Daylight Savings Time was active, and the Date object was automatically correcting my mistake by adding an hour to my time and displaying EDT.