Returns the current date and time in datetime format.
The NOW function is useful when you need to display the current date and time on a worksheet or calculate a value based on the current date and time, and have that value updated each time you open the worksheet.
In contrast to Microsoft Excel, which stores dates and times as serial numbers, DAX uses a datetime format to work with dates. Dates that are not in this format are implicitly converted when you use dates and times in a formula.
The result of the NOW function changes only when the column that contains the formula is refreshed. It is not updated continuously.
The TODAY function returns the same date but is not precise with regard to time; the time returned is always 12:00:00 AM and only the date is updated.