I have to update the Value in field in Order object using field update in workflow Rule

Updated field value should be:

Account JDE Shipto number- YYMMDDHHmmSS

like this format

for that i am using Formula field editor to populate the Value

but it is showing error, what i have to give in the Datetimevalue(expression) please anyone guide me for the Answer

I need to set a field on the Order object using a Workflow Field Update, and the updated value should be formatted as follows:

<Account JDE Ship to number> - YYMMDDHHmmSS 

I have tried to the following formula:

Account.JDE_ship_to_account_no__c - DATETIMEVALUE()

But the formula editor gives me this error:

Error: Incorrect number of parameters for function 'DATETIMEVALUE()'.` Expected 1, received 0

How can I make this field update work?