Display timezone values according to date created or current date.

Hello, I have a drop down field 'Time Zone' which contains options such as EDT, EST, PDT, PST. I have a few automatic functions I need to develop using these options. 

1. I want to display only PDT, EDT, MDT, AKDT, HDT options when daylight saving time occurs and when it is not daylight savings, I need to display PST, EST, MST, AKST and HST options in the drop down. 

2. There are two time of the day fields. 'Intended Arrival Time' and ' Time of Action', which are populated manually. When 'Intended Arrival Time' field is of a given value, I need to change the value of 'Time of Action' field to Arizona time according to the time zone and daylight savings. 

What formula should I use or any special fields to achieve this objective?

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Raj Helaiya
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