Hi theworkerplacecenter, and welcome to the forum 
allowedFromDate and allowedUntilDate define the absolute time frame in which these access restrictions apply. If you wished to provide access at various times during the month of January, you would set these date fields to the beginning and end of January respectively.
allowedFromTime and allowedUntilTime allow you to restrict the access on the individual days, e.g. 8am - 2pm in your first use case.
allowedWeekDays are the applicable days of the week this access is granted; this is set via bitmask (you find more information on that in the API documentation; it’s explained in “9. Create a keypad code with recurring access time”)
Hopefully that helps! Let me know if anything is unclear.