Hi Guys.

I am trying to have a formula field for the Week Number of the year. So, if opportunity is created on the 3rd January 2016, it would show "Week 1 2016".
I use the report in the Matrix format.
Currently, the field I am using for week number calculation is called "Created Date"
Format of the field is: DD/MM/YYYY (this was changed in the regional settings from the american MM/DD/YYYY format)

I have browsed forums and found many formulas... which none of them work.
One of them, for example:

MOD(FLOOR((Created_Date__c - DATEVALUE( "2016-01-01 " ) ) / 7 ), 52) + 1

It gives me the following error:
Error: Invalid custom summary formula definition: Field Created_Date__c does not exist. Check spelling.

Now, I am new in SFDC formulas, so as far as I understand, there is no such field. It should be called Crated Date. But if i use just Created Date - I get error that there is no field Created. If I use formula like this:

MOD(FLOOR(("Created Date" - DATEVALUE( "2016-01-01 " ) ) / 7 ), 52) + 1

I get error: Error: Invalid custom summary formula definition: Incorrect parameter type for operator '-'. Expected Number, Date, DateTime, received Text.

I know that I am doing mistake somewhere, but where?
Thank you for the answers!

Hi Guys.

I am trying to have a formula field for the Week Number of the year. So, if opportunity is created on the 3rd January 2016, it would show "Week 1 2016".
I use the report in the Matrix format.
Currently, the field I am using for week number calculation is called "Created Date"
Format of the field is: DD/MM/YYYY (this was changed in the regional settings from the american MM/DD/YYYY format)

I have browsed forums and found many formulas... which none of them work.
One of them, for example:

MOD(FLOOR((Created_Date__c - DATEVALUE( "2016-01-01 " ) ) / 7 ), 52) + 1

It gives me the following error:
Error: Invalid custom summary formula definition: Field Created_Date__c does not exist. Check spelling.

Now, I am new in SFDC formulas, so as far as I understand, there is no such field. It should be called Crated Date. But if i use just Created Date - I get error that there is no field Created. If I use formula like this:

MOD(FLOOR(("Created Date" - DATEVALUE( "2016-01-01 " ) ) / 7 ), 52) + 1

I get error: Error: Invalid custom summary formula definition: Incorrect parameter type for operator '-'. Expected Number, Date, DateTime, received Text.

I know that I am doing mistake somewhere, but where?
Thank you for the answers!