I think that you will find that if you sum the years, months and days then
the result will never be totally accurate because you would need to take into
account the month of the year each of the individuals commenced and finished
so that you know how many days the months represent because of the differing
number of days in the months. Of course for the individual the result you
have is accurate but it will not be accurate when you start to sum them.

I think that you will be better to simply create a column where you find the
Datedif in days (or simply subtract the start date from finish date) for the
individuals and format the cell to numeric. You can then sum the numeric days
and divide by 365.25 and I am sure that the result in years and decimals will
suffice for your needs.

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Regards,

OssieMac