Xslt conversion for dateTime in different timezone with day light saving - xslt

Question

Looking for some help on xslt conversion for dateTime in different timezone with day light saving. How to handle EST vs EDT while doing dateTime conversion in xslt?
enter code here
Below is one Sample order xml which will be converted into another order format <salesOrders> using xslt.
All dates in the "salesOrders" are supposed to be stored in GMT timezone.
<!-- Input orders xml -->
<xml>
<orders>
<order>
<order_id>1</order_id>
<!--lots of other details -->
<order_dateTime>2019/03/09 14:00</order_dateTime> <!-- yyyy/MM/dd hh24:mm-->
<order_timezone>America/New_York</order_timezone>
<!-- This time does not fall under day light saving ( UTC -0500) -->
</order>
<order>
<order_id>2</order_id>
<!--lots of other details -->
<order_dateTime>2019/03/10 14:00</order_dateTime>
<order_timezone>America/New_York</order_timezone>
<!-- This time falls under day light saving timing ( UTC -0400) -->
</order>
<order>
<order_id>3</order_id>
<!--lots of other details -->
<order_dateTime>2019/03/10 14:00</order_dateTime>
<!-- format : yyyy/MM/dd hh24:mm-->
<order_timezone>Asia/Kolkata</order_timezone>
<!-- Indian Standard Time ( UTC +0530) -->
</order>
</orders>
</xml>
<!-- after xslt conversion, the date should be converted as given below. -->
<xml>
<salesOrders>
<salesOrder>
<salesOrderId>1</salesOrderId>
<!-- required details -->
<salesOrderDttm>2019-03-09T19:00:00</salesOrderDttm> <!-- (14 + 5:00) -->
<!-- converted the time into GMT (-04:30)-->
</salesOrder>
<salesOrder>
<salesOrderId>2</salesOrderId>
<!-- required details -->
<salesOrderDttm>2019-03-09T18:00:00</salesOrderDttm> <!-- (14 + 4:00) -->
<!-- converted the time into GMT (-05:30)-->
</salesOrder>
<salesOrder>
<salesOrderId>2</salesOrderId>
<salesOrderDttm>2019-03-09T08:30:00</salesOrderDttm> <!-- (14 - 5:30) -->
</salesOrder>
</salesOrders>
</xml>
Need help for pupulating content of "salesOrderDttm"
The content of <orderDateTime> and <orderTimeZone> will be used to populate <salesOrderDttm>.
As mentioned above, it will be maintained in GMT (offset +0000) timezone.
The main problem is, same Time zone being treated differently. At one time(first order), offset is +5:00 and at another time(2nd order) the offset is +04:30
How to do it in xslt?
Came across adjust-dateTime-to-timezone() function, but that also expects us to provide the offset.
Is there any way to handle it?
I hope this is a very common problem and must be solved
Saw this post, but all it says it is not possible what I am looking for.
Similar query on stack overflow

Answer 1

In XSLT 3.0 you can achieve this using the $place argument of the format-dateTime() function. Quoting from the Functions and Operators spec §9.8.4
If the $place argument is supplied in the form of an IANA timezone
name that is recognized by the implementation, then the date or time
being formatted is adjusted to the timezone offset applicable in that
timezone. For example, if the xs:dateTime value 2010-02-15T12:00:00Z
is formatted with the $place argument set to America/New_York, then
the output will be as if the value 2010-02-15T07:00:00-05:00 had been
supplied. This adjustment takes daylight savings time into account
where possible; if the date in question falls during daylight savings
time in New York, then it is adjusted to timezone offset -PT4H rather
than -PT5H. Adjustment using daylight savings time is only possible
where the value includes a date, and where the date is within the
range covered by the timezone database.
Note that the way this is phrased gives implementations the option to "not recognize" timezone names; but let's assume they do.
First of course you need to convert 2019/03/09 14:00 to the xs:dateTime value 2019-03-09T14:00:00Z, which is a simple bit of string manipulation.
Now you can determine the timezone offset for America/New_York by doing format-time(xs:dateTime('2019-03-09T00:00:00'), '[Z]', (), (), 'America/New_York'), which will give you a value such as "-05:00" (as a string). You can convert this to a dayTimeDuration -PT05H00M using more simple string manipulation, and then use adjustDateTimeToTimezone() to apply this displacement to your original date/time value.
The XSLT 2.0 version of format-dateTime() does not have this capability defined.