count months looking at a list of dates

[psrs0810]

I need a formula that will tell me the number of month based on the list of dates:
e.g.

10/10/2014

10/24/2014

11/7/2014

11/21/2014

12/5/2014

12/19/2014

1/2/2015

1/16/2015

1/30/2015

2/13/2015

2/27/2015

3/13/2015

3/27/2015

4/10/2015

4/24/2015

5/8/2015

5/22/2015

6/5/2015

6/19/2015 I want to know that I have 9 months

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[Jonmo1]

Try
=DATEDIF(EOMONTH(MIN(A1:A23),-1),EOMONTH(MAX(A1:A23),0)+1,"m")

 

[Jonmo1]

It now seems I may have misunderstood the requirement.

Not necessarily, I could see drawing either conclusion based on the information given.
More complete issue description would help determine which method is better suited to the task.

 

[Kobraz]

This is a solution like the one Mike posted (in Norwegian):

=SUMMER(HVIS(FREKVENS(B2:B8;B2:B8)>0;1;0))

This formula counts how many unique months you got in your list after doing what you did in my last post.

 

[psrs0810]

bascually I am looking for is a formula that I will have a starting point that is going to calculate out every two weeks. It may go for 6 months to 16 months.
so if my starting point is 9/5/2014 and I see every two weeks ending 6/26/2015, I would want to know that there were 10 months in that timeframe

 

[Jonmo1]

It may go for 6 months to 16 months.

That eliminates Mike's solution, his would top out at 12.

And given that the dates are every 2 weeks, then there would be 0 months NOT included in the list.
So using the earliest date to the latest date should be an accurate count.

Test the last one in post #11

 

[psrs0810]

Thank you everyone

 

[Jonmo1]

You're welcome.

One last thing to note about the formula,
Make sure there are no 0's in the list of dates, you would get a hugely inaccurate result.
Blanks are ok, but no 0's.

 

[barry houdini]

FWIW This "array formula" will count the number of different months represented, it doesn't matter if there are gaps or if the dates are in different years

=SUM(IF(FREQUENCY(AE10:AE31,AE10:AE3-DAY(AE10:AE3)+1),1))

confirm with CTRL+SHIFT+ENTER

 

[barry houdini]

=DATEDIF(EOMONTH(MIN(A1:A23),-1),EOMONTH(MAX(A1:A23),0)+1,"m")

For the "no gaps" solution you can remove one of the EOMONTH functions if you revise the syntax a little

=DATEDIF(EOMONTH(MIN(A1:A23),-1)+1,MAX(A1:A23),"m")+1