How do I get the unique number of days in a datetime column in Google Spreadsheets?

Question

I have a column full of datetime values in a Google Spreadsheet.

I want to get a count of how many unique days there are. As in 8pm and 7pm today would count as 1. Tomorrow at 9pm, 3pm and 4pm would also count as 1.

Answer 1

Assuming your dates are in A1:A30, the following array formula worked for me:

=ArrayFormula(COUNTUNIQUE(TEXT(A1:A30,"yyyymmdd")))