Thanks to all for your responses. Here is the final answer that I have concluded after reading your messages and consulting with my sources. This is a recap of the final conversation I had with an institutional trader on this subject.
"Some charting software utilize BOM to accommodate retail traders who use candlestick price charts for TA which makes up a large percentage of their biz. As I understand it, most candle traders prefer the time stamp at the beginning of the chart bar for various reasons which may, or may not, be valid; you'll have to ask them. In contrast, some charting software utilize EOM to accommodate institutional traders because they are more likely to perform TA on historical data and need accurate time stamps on the chart bars correlating to the real clock/time.
As you have found out, all "historical" data on SC and other trading software which utilize BOM are "technically" incorrect because their respective chart bars are one-minute behind the clock and, therefore, they don't align with the actual real time that the chart bar occurred. However, it's important to note, that the "current" chart bar on all real-time trading software platforms which utilize BOM are correct with the clock, just like EOM charting software, that is, until the seconds hit 0:59 at which time, the BOM current chart bar becomes the prior chart bar and now that BOM prior chart bar is off by one-minute.
As long as a person is only using one charting software like SC then, this would probably be a nothing-burger because the retail trader would never know that the historical chart bar time stamps are off by one minute unless, they referred to the open/close price which are also off by one minute in which case, that might be cause for confusion. Other than that, the problem only becomes evident when a trader uses two or more charting services that calculate their chart bar times differently, such as in your case, because the BOM and EOM historical chart bar times will not correlate unless you add one minute to the BOM historical time stamps or subtract one minute from the EOM time stamps.
As far as to which method, BOM or EOM, of calculating chart bar times is industry standard? Without doubt, all the stock market indexes utilize EOM because you can't change the time on a clock. Otherwise, the markets would open at 9:29 ET and close at 3:59 ET (BOM time) which wouldn't make much sense. But that does not negate the reasons that SC or other BOM trading software companies may have chosen to utilize BOM in lieu of EOM as stated above.
What is amazing is that we're even having to have this discussion in the 21st Century. You would think that the charting software companies would give you an option to choose either BOM starting time or EOM ending time which would accommodate all traders and eliminate any potential issues."
"Some charting software utilize BOM to accommodate retail traders who use candlestick price charts for TA which makes up a large percentage of their biz. As I understand it, most candle traders prefer the time stamp at the beginning of the chart bar for various reasons which may, or may not, be valid; you'll have to ask them. In contrast, some charting software utilize EOM to accommodate institutional traders because they are more likely to perform TA on historical data and need accurate time stamps on the chart bars correlating to the real clock/time.
As you have found out, all "historical" data on SC and other trading software which utilize BOM are "technically" incorrect because their respective chart bars are one-minute behind the clock and, therefore, they don't align with the actual real time that the chart bar occurred. However, it's important to note, that the "current" chart bar on all real-time trading software platforms which utilize BOM are correct with the clock, just like EOM charting software, that is, until the seconds hit 0:59 at which time, the BOM current chart bar becomes the prior chart bar and now that BOM prior chart bar is off by one-minute.
As long as a person is only using one charting software like SC then, this would probably be a nothing-burger because the retail trader would never know that the historical chart bar time stamps are off by one minute unless, they referred to the open/close price which are also off by one minute in which case, that might be cause for confusion. Other than that, the problem only becomes evident when a trader uses two or more charting services that calculate their chart bar times differently, such as in your case, because the BOM and EOM historical chart bar times will not correlate unless you add one minute to the BOM historical time stamps or subtract one minute from the EOM time stamps.
As far as to which method, BOM or EOM, of calculating chart bar times is industry standard? Without doubt, all the stock market indexes utilize EOM because you can't change the time on a clock. Otherwise, the markets would open at 9:29 ET and close at 3:59 ET (BOM time) which wouldn't make much sense. But that does not negate the reasons that SC or other BOM trading software companies may have chosen to utilize BOM in lieu of EOM as stated above.
What is amazing is that we're even having to have this discussion in the 21st Century. You would think that the charting software companies would give you an option to choose either BOM starting time or EOM ending time which would accommodate all traders and eliminate any potential issues."
I just used that as an example as it's one of many indicators we use.