Q: What is the default(starting) time point to begin next (new) day checking?
A: It doesn't really work in that way. Each item would have its own time. You can essentially click on the history link of an item and see "Last Time an Item was Checked" and then you would know that the item would be getting checked again based on your Run Checker Every Setting in your General Settings.
For example, you can check the item's history (note it displays 0 hrs ago).
In your General settings, you have a repricing time (every 3 hours, every 1 hour, etc.), so the item would not be getting checked again until the next repricing schedule according to this timeframe.
Note: All times are displayed in Central Standard Time (US).
