the function date:add('1970-01-01T00:00:00.000Z', date:duration($currMillis div 1000)) returns the date in GMT time zone. how to get the date and time in the EST time zone.

The functions you refer to look like extension functions, not base XSLT functions, so I can't really help you without knowing what technology you are using.

However, the obvious guess would be to use a date in timezone -05:00 (if that's what you mean by EST) rather than one in timezone Z as the first argument.

XSLT 2.0 gives you lots of control over dates, times, and timezones, without resorting to extension functions.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference