I know this has been reported before but not in this current update. I went to create a new world when I did the sunrise and regular day rapidly flared back and forth as the day continued in Minecraft it did the same. I went to check if it was just that world but it was happening on all my worlds. I have a video if it is needed.
If it has been reported before, comment on the report that it affects 1.13 instead of making a duplicate report.