So, you're playing your favourite game. A rather addictive game. But you notice something weird. Even though you've been playing this game for months now (and you know that a similar amount of time has passed in-game), the day night cycles always trigger at the exact same time or, in other words, the length of night and day doesn't change. It's convenient certainly but this obviously doesn't happen in real life - there's a certain thing called seasons.
Congratulations! Your game's world uses an Eternal Equinox. This is when no matter what latitude or time of year it is, the lengths of night and day do not visibly change, no matter where you go or how much in-game time you spend.
However, notice this is not a prerequisite, nor does the game in question have to use real-time or clocks of any sort. All it has to do is to have the apparent lengths of day and night be constants.
If it's assumed that everything happens on equatorial latitudes, it can be considered Truth in Television. The length of the day on such places varies by much less than one hour throughout the year. This goes completely unnoticed by locals, unlike the actual climate variation, which is influenced by sea and wind currents among other things.
- Averted in The Legend of Zelda: Majora's Mask, given that it uses a day/night cycle, but takes place over only during an interval of three days, so there wouldn't be as much noticeable variation in times for sunset and sunrise. Played straight in Ocarina of Time, Wind Waker, Twilight Princess, and Breath of the Wild, which also have day and night. Skyward Sword has both day and night, but you never see the transition from one to the other (since you can only change time by sleeping), so it's unknown if this is happening or not. The rest of the series takes place exclusively in daylight.
- Star Fox Adventures applies this to both the main planet (Sauria) and the satellite regions that were separated from it.
- Castlevania II: Simon's Quest: "The morning sun has vanquished the horrible night." Even stranger, there is no twilight period. It goes straight from day to night or vice versa.
- World of Warcraft has day and night changing at the same time (sunrise is at 5:30 AM and sunset is at 6:30 PM; those are Pacific time for non-Oceanic realms and Australian Eastern time for Oceanic realms), regardless of longitude or latitude. That is to say, the days are equally long in every part of the world regardless of the time of the year, and the sun rises all over the world simultaneously. The reason is because some spawns and events are only available during the day or at night, and Blizzard doesn't want to change their availability depending on the time of year.
- Averted in MUME (Multi Users in Middle Earth) - the length of day and night changes according to season.
- Day and night in Nexus Clash last exactly one hour each regardless of season. The in-universe explanation is that the cities that become Valhalla aren't really attached to their planets anymore and the day and night cycle are being faked by the Powers That Be. The real game-mechanics reason for this is that playing a Revenant usually depends on tracking the cycle to avoid the day and go out at night, and it'd be annoying if Revenant players had to keep track of a bunch of extra mechanics.
- The Jak and Daxter series doesn't actually have clocks, but the sun rises and sets in the same interval no matter where you are.
- Hearts of Iron II. Day and night does vary with latitude, so days are shorter in the Northern Hemisphere. But they're always shorter in the North - apparently it's always winter there.
- Hearts of Iron IV averts this however, as the duration of day and night at different latitudes varies over the year.
- Pokémon Gold and Silver/Crystal introduced a built-in clock that has mornings start at 4am and night start at 6pm. This is changed in Pokémon Black and White. The different times of day start and end at times dependent on the season. For example, daytime lasts from 9 am to 7 pm in the summer, but in the winter it lasts from 11 am to 4 pm.
- Planescape: Torment: Day and night always come at the same time. Justified because Sigil is mostly self-contained and doesn't even have visible sky, so the day/night cycle runs on magic.
- Betrayal at Krondor: There is an in-game clock (it even looks like a sundial!), but no in-game season changes that affect the transitions from day to night or back.
- Animal Crossing has sunset and sunrise always occurring at a set time, regardless of latitude or time of year.
- The Sims games, despite being taking place over a fairly long time in in-game days, uses a fixed day/night cycle throughout. This happens even in The Sims 2 Seasons. Even when in this expansion the seasons changes -and player can choose the seasons desired- with heat, rain and snow, the Earth position doesn't seem to affect the fixed day/night cycle duration.
- In every one of the Harvest Moon games, sunrise is 6 AM and sunset is 6 PM, regardless of season. Averted in IoH/SI. In those, the times of sunset vary depending on the season. Sunrise is less clear-cut.
- Euro Truck Simulator averts it to some degree. Sunset time does not change throughout the year, but does change depending on your latitude. Sunset happens sometime around 9 PM in southern Europe, around 10 or 11 PM in Great Britain, and never in Scandinavia.
- The Battle for Wesnoth does this. On the associated fora, it was first justified as the result of the granularity of the turns, but then pointed out that at it's apparent latitude and granularity, there should still be noticeable change, but kept as an Acceptable Break From Reality.
- The GTA games run on this trope - Every Real Life second is 1 in-game minute, night/day are always the same length.
- Survival mode in Minecraft. A full day/night cycle lasts twenty minutes: ten minutes for day, seven minutes for night, and ninety seconds for sunrise and sunset. Since dangerous monsters come out at night, it's good that the passage of time is reliable day after day.
- Averted in Don't Starve. Day/night times changes according to the season. In summer days are longer than nights and nights are longer than days in winter.
- Averted in Gangsters 2. Nights are longer during the winter month stages.
- The Truman Show was implied to have a constant, instant day/night cycle.
- Truth in Television for places on the equator, where days are always the same length and seasons don't really exist.
- Downplayed example on the poles, where the days and nights are always exactly six months long.
- Mercury has an axial tilt very close to zero, so you'd have to get extremely close to the poles to have a noticeable change in the length of a day.