30days before due date in google spreadsheet

Question

I have one spreadsheet in which i want to save reminder date which will be 30days before due date.

Please note that the original sheet on which i am working does not has columns "Start_Date" and "End_Date" which are highlighted in yellow color in the shared spreadsheet.

Please advice to set 30days before date based on "End_Day" column in shared spreadsheet?

The below is shared spreadsheet for reference

https://docs.google.com/spreadsheet/ccc?key=0AhrpdumTdTjYdENLeU8yWkpNQm93MDJvREl1M3Y1aHc

Thank you in advance.

Answer 1

To create a date from the day (G2), month (H2) and year (I2) columns:

F2: =DATE(I2;H2;G2)

To create a date 30 days less than the date you just generated (F2):

J2: =F2-30