TODAY function will return the item’s today datetime.
Data Type Returned
TODAY will return a date or a numeric value.
TODAY() will return the current date set on the browser.
TODAY()-lastedited will return the number of days since the item was last edited
Using the TODAY function in conjunction with ROUNDDOWN and item start to return 3 types of values which relate whether the start of the item is a week away, that week or a week ahead.
ROUNDDOWN(((start-DATE(2019,12,11))/7 – ROUNDDOWN((TODAY()-DATE(2019,12,11))/7) which will return the current week number from today’s date (assuming the week begins on a Monday), where 0 = this week, <0 = last week or earlier and >0 = next week or later.