One of
our
students asked this question on Facebook: I would like to know how to
calculate a
sum in a period of time where dates are involved. This
interesting problem can be solved either using the DSUM function
or Array
formulas. The DSUM
involves:

Copying the headers to a location below the data
leaving a
space 3-4 rows

Defining the condition or criteria under the labels
or
headers

The headers and the conditions become the 'criteria'
of the
DSUM function

For a range of dates you can copy the 'dates' header
twice
so that under the first header you define the start date and in the
other 'Dates' header you define the End date as shown in the training
video.

The use of the sum and if functions as an array are quite powerful
and
useful. Here you need to do the following:

The data under the headers is selected and given a
name.
This data then becomes the named range. For example the data under the
Dates header is selected and given the name 'dates' and the data under
the 'Values' header is given the name 'values'.

Now you write the formula in any cell where you wish
to get
the result (E5 or E6): =sum(if((Month=(dates)=6), values,0)). Then
press the 3 keys ctrl+shift+enter
simultaneously
from the keyboard to get the result for June. In case you don't do this
correctly you'll get the result '#value'!

Watch the video below to see how to use the dsum and array formulas to
solve the problem: