A1: 08/01/99, with Data Validity User defined =DAY(A1)=1, to ensure exclusive entry of a month's first only.
B1: 0 for Saturday. Friday is 6, Sunday 1. Why? =MOD(Date,7) gives this order of weekdays and can be used internationally.
Possible results: 4 or 5. Here: 4. Similar Page: 5030.htm
A1: from (any date, without Data Validity!)
A2: until (later date)
B1: see above