Time Zone Computation

All,



Seem to have hit a wall that I hope others have scaled before me and may be
able to help me over.



I have an event that has occurred in a specific city within the US. I know
the date and time of the event. The SOAP service I am working with uses the
"XMLGregorianCalendar Class" for its interface. The format is
"2018-12-28T13:15:05-05:00" where it is CCYY-MM-DD with a 'T' to separate
the date and time, followed by HH:MM:SS followed by a hyphen and then the
HH:MM off-set to GMT. If the off-set was static that would be great, but as
we all know thanks to Daylight Savings Time and Standard Daylight Time the
off-set changes twice each year. However, let us not forget the cities
and/or states where no change is made (like parts of Arizona).



So, my dilemma is this - based upon a specific date and time, in a specific
city/state, how can I compute the number of hours difference to GMT for that
moment?



I'll take anything that I can do within the System i (BTW, we are on O/S 7.2
in case of any release-specific solutions), or an off-platform SOAP/REST
service I can call, only if it is free. You know how those multi-billion
dollar corporations are on letting loose with a nickel for a paid service.



Merry Christmas (belated), Happy New Year (in advance), and Happy Holidays
(in general) to all, and as always, thanks in advance for any assistance.



Steve Meisinger