David,
Can I be a nit-picker?

In (4 - 2) we are have 4 minus 2 (or 4 subtract 2) but in -4 we are not
doing any subtraction, rather we are negating 4 (in -x this amounts to
changing the sign of x)
So I like to use the term "double negation" or "double unary negation" but
since negation is a unary op the middle word is redundant

Sorry, but in retirement I must be missing my students to pick on !!!
best wishes from Canada
--
Bernard

"David Biddulph" <groups [at] biddulph.org.uk wrote in message
...
If A2:B2 contain text which looks like dates, the double unary minus will
convert them to real dates.
Note also that your formula has an m that ought to be a comma.
Note also that "double unary" by itself isn't a very specific term:
-- is a double unary minus
++ would be a double unary plus.
--
David Biddulph

"Daren" wrote in message
...
Hello,

The AND statement is as follows:

=and(--d2--c2,--c2--b2m--b2--a2).

What's the purpose of the double unary here?

Thanks!