Years in Service Formula

Good Day,

We are struggling with getting a "Years in service" calculator to work, after having pulled all the formulas that could be found by previous posts, still no luck.

=IF(AND(MONTH([Start Date]1) >= MONTH(TODAY()), DAY([Start Date]1) > DAY(TODAY())), YEAR(TODAY()) - 1 - YEAR([Start Date]1), YEAR(TODAY()) - YEAR([Start Date]1))

This is a copy and paste from another post, which it appeared had worked for them.

Dates are formatted as 8/2/2017, have tried 08/02/2017

But I consistently get  #INVALIDDATATYPE

Any suggestions would be greatly appreciated.

Robert