Germany was in no shape to start a war of conquest prior to mid 1939 (and even in the OTL, the ods were slimm when it actually started.) So Germany could not have started war earlier and likely not later as well, given the preparing USSR, who had calculated it would start its own war in late 1942 at its latest, against Germany. So the timeframe for Germany is rougly between the OTL start and early 1941, just as in the OTL, or its would fce certain defeat by the USSR, if starting later, given the Soviet numerical superiority in most fields after late 1942, especially with an intact warindustry running at full speed by then.
Japan too would not likely start its war earlier, as it was not prepared to do that politically, given its demands in China and the not yet seriously felt embargo on fuel and weapons. Starting later was perhaps a possibility, but not much later, but still within the same time Germany was fighting its own war. It depended on wether or not it would still attack the USA the way it did in the OTL, although that was just the sort of action typically done by Japan at all times, when starting a war against a strong opponent.