Finding missing dates in column

Assume your source dates are running in A1 down (dates must be real dates recognized by Excel)
Assume that the earliest date in col A will be the presumed startdate and the latest date, the presumed enddate
In B1:
=IF(ROWS($1:1)>MAX(A:A)-MIN(A:A)+1,"",IF(ISNUMBER(MATCH(MIN(A:A)+ROWS($1:1)-1,A:A,0)),"",MIN(A:A)+ROWS($1:1)-1))

In C1: =IF(ROWS($1:1)>COUNT(B:B),"",SMALL(B:B,ROWS($1:1)))
Copy B1:C1 down until blanks appear continuously in col B  
Format col C as dates. Col C will return all the missing dates, neatly packed at the top 

One method of noting non-sequential dates would be through the use of Conditional Formatting (CF) to highlight cell containing dates out of sequence.

Suppose your column of dates in in column A with the first date in A1 and the entire range of dates is A1:A100. Select A2:A100(not A1:A100), then use CF to create a new rule. Select Use a formula to determine which cells to format, then put this formula into Format values where this formula is true:.

=A2<>(A1+1)

... and click the Format... button to select cell highlighting, etc. Click OK on the way out to accept the new rule.

Any date that is not 1 day higher than the one above it should exhibit the highlighting you chose.

• "Have you tried turning it off and then on again?" - Roy from 'The IT Crowd' (Emmy award-winning British comedy)