A day is a 24 hour period that includes a time of sun and a time of darkness. Usually a day starts immediately after midnight, and it does not end until midnight 24 hours later. Sometimes the word day is used to refer to the period in between when the sun rises and when it sets again.
Days should speak, and multitude of years should teach wisdom (Job 32:7)
Don't be fooled by the calendar. There are only as many days in the year as you make use of