Days between dates: DATEDIF and NETWORKDAYS
Subtracting two dates gives calendar days: =C2-B2. For anything else there are functions.
DATEDIF(start, end, unit) counts whole units: "Y" years, "M" months, "D" days. "YM" gives the months left over after whole years, so tenure reads "7 years and 4 months". If the start is after the end, DATEDIF returns #NUM!.NETWORKDAYS(start, end, holidays) counts Monday to Friday, both ends included, minus any dates in the holidays range.WORKDAY(start, days, holidays) returns the date that many working days later: a due date that skips weekends and holidays.
Keep "today" in a cell, such as a report date, rather than calling TODAY() everywhere: the numbers then stay the same while you check them.
=DATEDIF(B2, $F$1, "Y")
=NETWORKDAYS(B2, C2, Holidays!$A$2:$A$5)
=WORKDAY(B2, 10, Holidays!$A$2:$A$5)
Whole years of service; working days in a task; a due date 10 working days out.