This is my attempt of making what some mods do but in vanilla Minecraft with a datapack,
This Datapack Extend the length of time of a day up to 24h like in real life,
This does not synchronize your computer clock to Minecraft. You have to do it manually.

Features:

-Extend the time of the day to 24H,

-Time Display by holding a clock in your hand, also work when holding with second hand,

-This pack also have a function to set the time of the day by yourself to help you synchronize your Minecraft world to real time:
/function antor:longer_days/set

See How to Use it

Note: Minecraft has a feature that when Sleeping in the bed will not skip the night when Daylight Cycle is disabled. Which goes well with Longer Days intent to not skip the night.

Installation:
Just add the datapack to the datapack folder for your world when creating it or after being created
what will happen when enabled is the gamerule DodaylightCycle will be automatically disabled and do the job.

Uninstallation:
To uninstall the datapack and turn your world back to normal, Type the command /function antor:longerdays/uninstall.
After entering the command, all scorboard related to Longer Days will be removed, Longer Days will be disabled, and the game will suggest to you to enable the gamerule DodaylightCycle back to true.

I recommend disabling the gamerule "sendCommandFeedback".
It works on a solo world, but you will need to set the time every time you start a new session (and pressing pause) and work better on a multiplayer world that is active 24h/24.

Longer Days [DataPack]