Turn changes (also known as game ticks) are the basic unit of time in Nations. Important events happen during the turn change, ranging from production to deployment of units. There are many different intervals of the turn changes, the smallest lasting a measly 10 minutes with the largest turn changes last a whole hour (though day changes could also be argued to be a turn).
10 Minute Ticks
All "ten minute ticks" occur on the ten minute marks (1:10, 1:20, 1:30 etc). All changes that occur every ten minutes happen at set times.
Every ten minutes, one 6th of your total military's upkeep is taken. If your food upkeep is 6, then every 10 minutes you will lose one food.
Every ten minutes tick, if a unit requires healing, double of the hourly uptake for that unit is taken to heal 10% of its base HP.
All peacekeeping missions are sent at ten minute ticks. Divisions sent at 2:11 and 2:19 will both start their peacekeeping mission at 2:20.
This also applies the other way, when divisions are returning from peacekeeping missions. Divisions that finish their battles at 2:41 and 2:49 will both be back, ready to be sent elsewhere at 2:50.
Hour Game Changes
0 past the hour (GMT)
At the hour, every hour, your population upkeep will be used up, what consists of money (government if not Dictatorship, though money would be given then), power, and Consumer Goods.
At this stage, all things on your queue will go down an hour, and if less than hour, or complete, so it would be viable to build things at 7:59 am and 7:20 am (GMT/UTC), as they would be 'done' at the same time.
Another use of this ticks is for offers, all offers whether it be unit, officer, item shop or card pack shop, it would be timed against this, the time til the beginning, time remaining and ending of all sales will happen at this time too.
(Due to this many actions happening at this point, including all the 10 minute ticks, there may be a lag spike at this time)
(As far as I can remember,) no other uses of ticks at this time
30 Minutes past the hour
The only use of this tick is Foreign intelligence, where you lose your money at this time, and an hour 'passes'.
There is no tick for all factories, and all act independently, producing every half an hour exactly.
This is when all quests reset, you are allowed to Expand border again, events are generated (though will start the next time you log in), and Sales generate (there may be others). Due to so many things being updated at this point, there may be a delay at this point also
DM me on discord or say in the comments if there any others