Side effect of UnixToISO()

To reproduce the bug, local timezone should not be set to UTC.

Script below produces datetime strings and hour numbers in local timezone:

in = load 'in' as (ts: long);
out = foreach in generate ToDate(ts), GetHour(ToDate(ts));
dump out;

(For input 0 result is (1970-01-01T03:00:00.000+03:00,3) on my machine.)

If UnixToISO() is called nearby, builtin ToDate() changes output, producing result in UTC timezone:

register piggybank.jar;
DEFINE UnixToISO org.apache.pig.piggybank.evaluation.datetime.convert.UnixToISO();

in = load 'in' as (ts: long);
out = foreach in generate UnixToISO(ts), ToDate(ts), GetHour(ToDate(ts));
dump out;

(For input 0 result is (1970-01-01T00:00:00.000Z,1970-01-01T00:00:00.000Z,0) on my machine.)