Times displayed are in the local time zone and style (12-hour or 24-hour) used by your computer. That includes whether the time is standard time or daylight saving time.
If the time seems to jump by an hour from what you expect, it may be that the time changed from standard to daylight or vice versa. We try to note this, but not all browsers may do so correctly.
Currently the output always starts today.
We assume you are awake when entering data. In other words your wake time is in the past and your bedtime is in the future. If you are doing this for someone else who is in their sleep phase, that assumption may not be correct. You will have to wait until they are awake.