Get correct datetime from Oracle query via ROracle in R

As you mentioned this is a timezone conversion which R is doing as per local timezone. For more details you can refer this link

http://www.oralytics.com/2015/05/r-roracle-and-oracle-date-formats_27.html

Try setting these system variables before connecting through ROracle

Sys.setenv(TZ = "GMT")
Sys.setenv(ORA_SDTZ = "GMT")