Mmh - you can do it, at least I have a workaround for you. Here is what I did to manage a time calculation for a PI Trend:
1. I created an OLEDB data set in the PI data services admin:
SELECT ? + ' - 1h' StartTime, ? + ' + 1h' EndTime
As you can imagine, the two placeholders are Text.
2. I added a PI Table web part and connected the time series web part to this one, passing the timestamp to the two place holders
3. I connected the two columns from the table web part to the trend to pass the start and end times.
That's fantastic, thanks for that.
Below is what I have so far. Only thing I've found however is that I have to select the row in RtTable part for it to send that start & end time to the Trend part. Ideally I'd like to hide that part. Is there any way to auto select a row and have it flow through when I select a row in the TimeSeries part?