time() - _indextime,
1. but I want to be using what the user has selected from time range picker
2. if time picker local time is different from index time, how to make sure that is cordinated & used instead of what the server time.
Without seeing your full search, to see what exact calculations are being performed, I can only say that, you can use command addinfo to get the value from timerange picker to your search result. Example,
The two (out of 4 total) fields that this command adds, info_min_time which contains the earliest and info_max_time contains the latest value of time range picker. See this for more information on this command.