conditional formatting, dates calculation

O and P are formula generated dates from AD and AE in another spreadsheet using

=IF('Contract activity'!AE2=0,"",TEXT('Contract activity'!AE2,"d mmm yy")) and
=IF('Contract activity'!AH2=0,"",TEXT(('Contract activity'!AH2),"d mmm yy"))

I want to highlight when P comes a day after O, so I have conditional formatting for

=ROUNDDOWN('Contract activity'!AH2,0)=(ROUNDDOWN('Contract activity'!AE2,0)+1)

Normally it works but not always. 30 June 2013 to 1 July 2013 doesn't highlight. Neither does 29 Nov 2014 to 30 Nov 2014. Why?

I've tried using the same conditional format and it seems to work fine for the dates listed. Maybe attach a sample spreadsheet?

I removed some data for confidentiality but rows 1, 17, 25, 28, 40, 42, and 50 should all be green. Otherwise conditional formatting and info in A-B all reads direct from worksheet 'Contract Activity' to simplify the numbers.

Could I also do this by creating a column in between? The original data is on 'Contract Activity'. I could make another column with =INT(AH2), and have my conditional formatting refer to this instead?