There are TWO ways to purchase data:
For those of you with your own asci csv ot txt data this video may prove informative. Watch how Portara and NinjaTrader handle DST and dual DST differences (for overseas markets) in unison. See the database change based on your current location.
Watch the differences when traders are based in different time zones such as Australia, the UK and the US with worked examples.
View this presentation to find out how it all fits together.