Table:
0
A
B
C
1
calendar date
day number
reference calendar
2
1972-03-31 09:47:22
5
3
1976-06-15 03:40:06
7
4
1985-05-13 12:19:43
7
5
1986-10-14 17:53:39
1
6
1987-11-05 06:11:22
3
7
1988-02-01 14:41:52
8
8
1994-11-15 03:49:54
9
9
1995-01-01 03:52:11
1
10
1997-03-10 15:24:00
7
11
2007-05-28 16:28:48
2
12
2008-06-08 12:45:38
3
13
2009-08-18 03:29:08
8
14
2010-11-26 19:22:50
7
15
2012-07-03 09:48:46
7
16
2017-01-06 23:17:22
8

Questions and formulas:
Question: How many different dates are there?
Formula: ROWS(UNIQUE(A1))
Formula2: ROWS(UNIQUE(A2:A16))
Level: easy
Question: What is the total number of days on each calendar date?
Formula: SUMMARIZE(A1,SUMX(B1))
Formula2: SUMMARIZE(A2:A16,SUMX(B2:B16))
Level: easy
Question: The number of days in total on each calendar date.
Formula: SUMMARIZE(A1,SUMX(B1))
Formula2: SUMMARIZE(A2:A16,SUMX(B2:B16))
Level: easy
Question: How many calendar dates?
Formula: ROWS(UNIQUE(A1))
Formula2: ROWS(UNIQUE(A2:A16))
Level: easy