Harvest-Festival-1.10.2-0.5.25
Changed:
I:"Ticks per day"=120000

When you start a new game with this setting, the sun is coming up on Spring Day 1 (Sun), but the time is stated as 1:20 (ish), not around 6:20, which is what it still should be. By the time the sun is at midday, it says it's Spring Day 2 Mon 21:30, while it should still be Spring Day 1 Sun 12:00. Then the sun hangs in the middle of the sky not moving for ages, until about Spring Day 2 Mon 1:20, when it suddenly flashes across the sky to sundown and says it's Spring Day 3 Tue 1:20.

Can you test this on 0.6. I changed the sun calculations there.

This happened to me as well, I had no chance but to change it back to how it was.

Tried adjusting ticks per day to 36,000 on a pre-existing world. Didn't notice the same issue but npcs seem confused and don't open shop at the appropriate times.
version 0.6.0-218