Round a number down to the next multiple

=FLOOR(number, significance)

Return the number of days between two dates

=DAYS(end_date,start_date)

Returns a vertical array of the most common values in a data set.

=MODE.MULT(number1, [number2], ...)

Return a random number between 0 and 1

=RAND()

Remove irregular spacing from either end of or within a text string.

TRIM(text)

Evaluate and return the contents of a reference specified by a text string

=INDIRECT(ref_text, [a1])

Return the value or reference of specified cell(s)

Array form: =INDEX(array, row_num, [column_num])

Reference form: =INDEX(reference, row_num, [column_num], [area_num])

Return a reference that is a specified number of rows and columns from a starting point

=OFFSET(reference, rows, cols, [height], [width])

Return the absolute value of a number

=ABS(number)

Return the reverse of TRUE or FALSE statements based on testing logical conditions

=NOT(logical)

Return the year, month or day component of a date

=YEAR(serial_number), =MONTH(serial_number), =DAY(serial_number)

Sum (add) values together.

=SUM(number1,number2,…)

Return the serial number of a particular date

=DATE (year, month, day)

Return the rank of a number in a data set

=RANK.AVG(number,ref,[order])