Bar Time Stamp
NinjaTrader stamps a bar with the closing time of the bar. For example, a minute bar with a time of 9:31:00 AM has data from 9:30:00 AM through 9:30:59 AM. Using end of bar time stamps is required in order to be able to plot multiple series of differing time frames within a single chart all accurately synchronized to time.
Discrepancies Between Different Data Feeds
Different data feeds produce different charts, especially when using tick based intervals vs time based intervals. Market data vendors each employ various methods for tick filtering, throttling and time stamping. As a result, no data stream is 100% identical and thus can cause subtle differences in charts. Since NinjaTrader supports many of the leading brokerage and data feed technologies, it is highly likely that two traders using NinjaTrader on different data feeds will have minor differences when plotting the same market and time interval.
Different session templates as well as the date range of data being plotted can affect the chart display and indicator values.
Real-Time Tick Filter
If you have the real-time tick filter enabled, it is possible that your offset percent (the percent away a tick is in value from the last traded price to be considered a bad tick) may be too tight and thus a good tick (gap up/down on session open for example) could be excluded from the bar.