What Minecraft actually records
In Minecraft: Java Edition, pause the game and open Statistics. Under the General tab you will find entries including time played and time since last death. That figure belongs to the current world save, not to you.
Bedrock Edition exposes far less. Some statistics are available through the pause menu depending on version and platform, and Xbox profile statistics may report time played for the Bedrock title if it reports them to Xbox services.
Why per-world statistics do not answer the question
A long-time Minecraft player has a dozen single-player worlds, several deleted ones, hundreds of hours on servers where the statistics belong to the server, and years across different versions and installations. To get a lifetime total from the statistics screen you would need every world you ever created, still present, and you would still be missing all multiplayer time.
Realms, modded instances through launchers like CurseForge, Prism, or MultiMC, and older installations each fragment the record further.
Modded and multi-instance setups
If you run modpacks, you probably have several separate instances, each with its own saves folder and its own statistics. That is a good setup for playing and a terrible one for knowing how much you play. Third-party launchers may show a per-instance figure, but nothing totals across them or includes vanilla play.
Track the Minecraft client itself
PlayCounter measures how long the game is running on Windows, which is the number people actually mean by "my Minecraft hours". Single-player, servers, Realms, and modded instances all count, because they are all the same client running.
A note on how Java Edition launches: the official launcher starts the game as a Java process, and modded launchers do the same with their own wrappers. Depending on the setup, PlayCounter may need a one-time confirmation to tie the running process to Minecraft. Once you have made that choice it is remembered locally and tracking is automatic.
As with everything else it records, sessions and totals stay in local app storage on your PC, no account is required, and Minecraft sits in the same list as the rest of your games so you can see where your time really goes.