What is the best way to measure sent/received traffic on an interface divided by month or week?
If I go to Interfaces then scroll to the bottom (on web interface) then I can see the data but I don't know since when did that traffic occur.

1. Statictics on interfaces cleared after reboot.
2. Correct way is use netflow (i.e.IP/Traffic Flow + something like ntopng/mrtg/prtg/cacti etc)
3. But for rough statistic some scripting can be done, like https://wiki.mikrotik.com/wiki/Scripts/ ... sermanager
or more advanced approach (do you remember about 1?) - https://aacable.wordpress.com/2015/03/09/5386/

I was looking into ntopng, that's a very nice thing however requires an nprobe which isn't feasible for me.
However I can look into the other things you posted, thank you!

ntop worked out nicely for me, has lots of useful information!