Store the time zone in the file as well and so when your application opens it in Prague you calculate what time offset you need to apply to the DBL and calculate the Sydney time.
Check out the following thread: http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=506500000008000000A6840000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0&USEARCHCONTEXT_TIER_0=0&USEARCHCONTEXT_TIER_S=0&USEARCHCONTEXT_QUESTION_0=UTC&USEARCHCONTEXT_QUESTION_S=0
