Afaik it is the same through the whole year. Regardless of month it indicates for example ~20 hours of daytime and ~4 hours of nighttime in northern finland/sweden/norway, which might be true for the summer, but surely isn´t in winter. I personally think that this is a minor issue but will use this opportunity to ask about a (imho) serious task
Will you look into the supply issue where troops get always supported from the first port captured? When fighting in western india as japan your troops still get supplied from shanghai/any port in china you captured in your china-campaign. Due to the low infrastructure of the yunnanregion this isn´t working very well. Sure, as a human player you are able to improve infrastructure over time to overcome this, but it would be more realistic/work for the ai too to have these troops supplied via the indian ports (mumbay/calcutta/etc) you captured. This may happen all around the world (allied invasion in spain supplying troops in germany/invasion of us mainland...), the situation in india will happen very often. Thanks in advance.
With Semper Fi you can set up convoy routes from and to any port which is more then a few provinces away from a depot allowing you to circumvent the poor infrastructure and keep your frontlines as supplied as the ports allow them to be. So yeah don't think that particular problem is an issue anymore.