SUM(...)
Counting an item for same dates but for last month
Used Functions
Category: Math and trigonometry
Adds its arguments
Syntax
SUM(number1,[number2],...)
Practice SUM Formula at Sheetzoom
SUM formula at Microsoft helpCategory: Date and time
Returns the serial number of the last day of the month before or after a specified number of months
Syntax
EOMONTH(start_date, months)
Category: Date and time
Converts a serial number to a day of the month
Syntax
DAY(serial_number)
0
The formula starts by getting the start date with EOMONTH that find the last corresponding month and DATE is used to get to the same date. The corresponding array of values is then summed up to give the count.