Sometimes we need to run some processes in the scripts on last N bar but currently we don't know bar_index value of realtime bar or number of remaining bars before we reached it. So most of us use "start date" as input and run some processes after "start date".
This experimental script finds last Nth bar approximately. As you can see in the script we (should) use GMT , otherwise as I see the result might not be accurate (we don't know timezone used on the chart)
The idea is to find/use similar bar in the past (using timenow as reference) and then calculate aproximate the time of last Nth bar. the results may not be accurate all the time, also we can not know local holidays etc.
At the moment the script works on 1minute or higher time frames (it won't work on less 1min timeframes)
In the future if the Pine Team add something like "bar_index_realtime" then we will not need such things. by the way many thanks to Pine Team, they are doing great job.
You can use this script in your scripts as you want, no need to ask permission. If you can improve it let me know ;)
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.