Date and Time
CDDA features the passage of time based on the number of turns taken by the player's character and other factors. Just like real life the game has a full day and night cycle, and seasons. The player can always tell what season it is and, while above ground, the character can always view the position of the sun. In order to tell the exact time, the character needs to have some kind of time-telling device in their possession.
The Passage of Time
Time passes based on player activity. Certain actions take more or less time than others, but they will always say how much time they take. Such activities include, reading, sleeping, movement, waiting, eating, crafting, construction, combat, and many others. The faster your character is at an activity, the slower time will pass. For example, a faster character will cover more ground in less time than a slower one. Your speed also effects how much other entities in the game world move. A fast character will see enemies and NPCs barely move as they do. A slow character will see enemies and NPCs basically teleporting, so keep this in mind. It is also important to note that the world has an "operational bubble." That is, the world is persistent, but things will only happen graphically while you are around to see it. Certain processes, such as rain water collection, won't happen while you are away but happen retroactively when you approach.
Night and Day
Keeping track of the time of day is imperative to your survival. Natural light is often your only light source for things like reading, crafting, and general movement. Therefore, daylight is often on your side. Eyesight at night is, understandably, limited. Unless you have a light source, or special traits, your vision will be limited to one tile. This makes navigation and detecting enemies very hard as well as any other task that requires light. Furthermore, enemies with night-vision will pick you off incredibly more easily at night. On the other hand enemies without night vision can be easier to avoid, or take on one at a time, for a character with a night-vision enabling, or enhancing, trait. In general though, night is a time for sleeping. People tend to stay alive that way (mostly).
There are two ways for a character to tell the time of day. The first is for them to look at the sky, and the second is to use some kind of device.
Looking at the sky (without a device)
As long as the character can see the sky (e.g. is not underground) they will see a small sundial pictograph in their UI display (seen at right). This picture will change throughout the day and night and corresponds to the hour of the day. It is impossible to tell the exact time without a device. If the character is underground (e.g. in a basement, etc.) the sundial will be replaced with the grey-tinted message "underground." This limits natural time telling to above-ground use.
Using a Device
Any device listed with time-telling capabilities in its description will display the exact time of day in the UI display as a digital clock. This replaces the sundial, and will continue as long as the device has power. Such devices include gold watches, PDAs, alarm clocks, clocks in cars, wrist watches, cell phones, and pocket watches, as well as bionic enhancement. This is a much more reliable and easy way of telling time than looking at the sky.
The four seasons are, as in real life, Spring, Summer, Fall, and Winter. The length of the seasons, in days, depends on the number the player inputs on the world-creation option screen. It is always possible for the player to tell the season regardless of being above or below ground. The season has an effect on plant growth and has an effect on the weather. Farmers and anyone hoping to travel outdoors should keep this in mind.
Seasons and farming
The four seasons control when food-bearing plants grow. Each season is divided in half, early and late.
Early spring-Wild plants don't give food, can't plant seeds (It's too cold to plant anything now.) Late spring-Wild plants don't give food, can plant seeds Early summer-1/2 wild plants give food (berries, apricots), can plant seeds Late summer-1/2 wild plants give food (berries, apricots), can plant seeds Early autumn-The other 1/2 wild plants give food (cherries, apples), can't plant seeds Late autumn-The other 1/2 wild plants give food (cherries, apples), can't plant seeds Early winter-Wild plants don't give food, can't plant seeds Late winter-Wild plants don't give food, can't plant seeds