Thats not possible in the moment. You have timeframe filters for dashboards and dashlets which allow you to define a certain time period, e.g: last year, last X months, last X months shifted by Y months, ... - but there is no option right now to say "Last Year excluding January!". What you can do is to define certain Incidents for a timeperiod, e.g: "First DAy in January". You can then use the Heat Field Option in charts to highlight that particular timeframe. Users will see a RED mark on top and can move their mouse over which would then show them something like "This was January 1st and we did a deployment".
If this is of interest check out the Heat Field Option and Custom Incidents which you can visualize up there
have you found any differences in 2017 version? is it possible to exclude periods of measurement? What happens for sheduled blackouts? how do you make to exclude them from aggregate measurements?