30 minute time increments randomly starts adding seconds

[MAP77]

I have 30 minute interval data (date and time) and I want to copy the date and time formula down the column so that it increments by 30 mins. The time format is hh/mm/ss and there are no seconds. This seems to work ok until randomly it starts adding seconds as well which requires you to stop and correct it back to 00 seconds and start copying again. It does this over and over at random intervals making it hard to copy when you have 20,000 plus cells to copy down.

It doesn't add seconds consecutively but will stay on 1 second for a while and then switch to 2 etc. slowly adding over the course of the formula copy down the page.

Any ideas on how to stop it from doing this?

 

[Toadstool]

Hi MAP77,

You don't say how you're adding the 30 minutes each time so try this method.

 

[MAP77]

Hi Toadstool,
I was just copying line 1 down and then changing line 2 to 30 mins, then scrolling that down. I've adjusted it to how you have suggested. Do you know if there is an easier way to copy the formula down than manually dragging it?

 

[horizonflame]

You can use filldown for this. Do you have data in Column A, B, C or D that indicates the last row being used?

 

[MAP77]

You can use filldown for this. Do you have data in Column A, B, C or D that indicates the last row being used?

Yes I have different data in those other columns. The last row across all columns is row 9889

 

[horizonflame]

Will that last row change or is it static?

 

[MAP77]

Will that last row change or is it static?

I've got the formula copied all the way down so I'm all good. Thanks for your help