How do I make a daynight cycle?

[Cffex]

I feel ashamed for not knowing how to do this as a 2 years experience scripter.

local run_service = game:GetService("RunService")
local lighting_service = game:GetService("Lighting")
local daylength = 15 --// Minutes

run_service.Heartbeat:Connect(function()
    --// I can't figure out the math so that a day lasts exactly 15 minutes.
end)

[AustnBlox (Austin)]

local Lighting = game:GetService("Lighting")
local RunService = game:GetService("RunService")

local MinutesPerSecond = 1 --1 second equivalent to 1 minute (1 day = 24 minutes).

local function OnHeartbeat(Delta)
	Lighting.ClockTime += (MinutesPerSecond / 60) * Delta
end

RunService.Heartbeat:Connect(OnHeartbeat)

[Cffex]

I want it to last 15 minutes, sure, I could change MinutesPerSecond but that would not be as simple as changing the daylength to any number I want. (Also I want to clarify that I suck at math)

[Cffex]

No one is responding screw this I’ll just use tween service

[Cffex]

Here is the code:

local lighting_service = game:GetService("Lighting")
local tween_service    = game:GetService("TweenService")
local daylength        = 15 --// Minutes

local tween = tween_service:Create(lighting_service, TweenInfo.new(daylength * 60), {
	ClockTime = 24
})

tween:Play()

tween.Completed:Connect(function()
	tween:Play()
end)

[Front3D]

Do you want a daynight cycle that lasts 15 minutes every day and night?

[Cffex]

I want a daynight cycle that makes every day last 15 minutes

[Cffex]

So night is 7.5 minutes and day is 7.5 minutes

[Front3D]

You basically want each morning and each night to last about 7.5 minutes

[Cffex]

That is not a daynight cycle, you manipulating brightness which doesn’t relate to daynight cycle

[Wigglyaa]

There are 1440 minutes per day.
If you want a daylength of 15m then each actual min is the same as (1440 / 15).
But you will want your function to run more smoothly than this so we work it out per second (1440 / daylength × 60).
This figure is the step change in minutes after midnight to add each second. But you’ll also need to remember to reset to 0 once it reaches 1440.
Hope that helps with the math.

[Cffex]

local run_service = game:GetService("RunService")
local lighting_service = game:GetService("Lighting")
local daylength = 15 --// Minutes
local total_minute = 1440

run_service.Heartbeat:Connect(function()
	local increment = daylength / total_minute
	lighting_service.ClockTime += increment
end)

I don’t understand what you mean by ‘But you will want your function to run more smoothly than this so we work it out per second (1440 / daylength × 60).’

[Dev_Peashie]

Why not using the delta of Heartbeat so the day last exactly the 15 minutes?

local run_service = game:GetService("RunService")
local lighting_service = game:GetService("Lighting")

local Desired = 1 -- 1 minute for testing, change it to 15
local perSec = (24/Desired)/60

run_service.Heartbeat:Connect(function(delta)
	lighting_service.ClockTime += perSec * delta
end)

[Wigglyaa]

The step change per minute will make the sun and moon jump across the sky.
Per second looks smoother, as it is many more smaller movements, and @Dev_Peashie suggested using the delta time for even greater precision and even more smaller movements.
The shorter your desired daylength, the more frequently you will want to adjust the lighting.

[Cffex]

I read the code and it made so much sense, thank you @Dev_Peashie and @Wigglyaa