This is a complete newbie questions - apologies. I don't have much experience with international travel from the US to Europe, Asia, South America, etc., and am wondering how far in advance airline tickets need to be purchased to get the optimum price. Not trying to be immensely specific, but in the US for example if you book at least 3-4 weeks out you'll be roughly on top of things. Obviously within 2 weeks prices will be quite a bit higher. I'm not sure if the same rationale applies to international travel.

I've done some initial investigation on google flights but holiday flight schedules are skewing data so I don't really have a good sense. I plan on doing a number of international flights in 2018, but the earliest may be Milan in March. I noticed last week flights were around $450 from Atlanta - now they're up to $650 or so. Not sure if that was a special, or if booking multiple months out really is that advantageous.

Thanks in advance.