Dates every 15 min show a Reference number

[shonaart]

Hi Guys

I have a Column A with dates & times eg: ( 2019/08/11 06:00 ) running, for example, continues for a number of days.
In Column B I would like to show a numerical number starting from 1 .... every 15min. So example from 19:12 to 19:27 column B with show a 1 then from 19:28 to 19:43 will show a 2 and so on every 15min etc

Column A
2019/08/04 Sun 19:12
2019/08/04 Sun 19:13
2019/08/04 Sun 19:18
2019/08/04 Sun 19:19
2019/08/04 Sun 19:20
2019/08/04 Sun 19:26
2019/08/04 Sun 19:27
2019/08/04 Sun 19:28
2019/08/04 Sun 19:33
2019/08/04 Sun 19:34
2019/08/04 Sun 19:38
2019/08/04 Sun 19:38
2019/08/04 Sun 19:39
2019/08/04 Sun 19:40
2019/08/04 Sun 19:42
2019/08/04 Sun 19:45
2019/08/04 Sun 19:45
2019/08/04 Sun 19:46
2019/08/04 Sun 19:46
2019/08/04 Sun 19:47

Maybe there another way of looking at this. What I am trying to achieve is to count how many dates & times ( Time stamp ) happens every 15 Minutes. So from 19:12 to 19:27 there were 7 timetamps and the second 15min it was 8 x timestamps. The Date& time is everytime a container was moved by a crane.


Thanks I would appreciate your help.

 

[shonaart]

Guys,
Is there way I can upload the Excel spreadsheet and then maybe you guys can help me.

Thanks