Original Summary: Jarring shift from morning to night a minute after waking up. World created in 23w45a, Game Mode: Hardcore

This bug was an issue with the weather and not the day/night cycle, as I originally thought when I first wrote this. I edited the report accordingly. Strikethrough words are from the original bug report and italicized words were added later on.

This incident took place in a Hardcore world I created in the 23w45a snapshot. In the "Experiments" tab, bundles are off, villager trade rebalance is off, but experimental 1.21 features are on. I was around a savanna village to collect acacia wood when this happened.

The sequence of events that took place:

• Slept inside one of the small savanna village houses visible in the screenshot
• Exited villager house
• Sprinted (with some jumps and slowdowns) in a direct line from the village to the place I'm standing in the screenshot
• Game instantly shifted from morning to night clear to thunder weather types as I approached where I'm standing
• Hostile mobs instantly spawned in around me (field was empty before shift to night took place)
• Pillared up from the spot I was standing
• Took attached screenshot

BUG: The weather in this savanna biome changed from clear weather to the thunder weather type in less than a second. Hostile mob spawning also didn't function as is intended, with all of the mobs appearing far quicker than normal when conditions change (i.e. day to night, or clear to thunder). There was no fade or transition going from clear weather to thunder. I didn't get a screenshot of the sky before the abrupt change happened, but it was bright and light blue with some clouds.

I went from casually sprinting to a forest at morning time in clear weather with no hostile mobs visible in the area, to the time the weather jarringly shifting to night a thunderstorm with hostile mobs appearing all around me. None of the hostile mobs near me in the screenshot have noticed I'm there but it's a strange bug I've never seen before.