Convert 15 minute data to 30 minute data

[Challis]

Hi,
I am looking to convert 15 minute data to 30minute data as below (for 1000s of rows):

1/01/2019 8:15	1801.669	1/01/2019 8:30	3602.79
1/01/2019 8:30	1801.121	1/01/2019 9:00	3606.543
1/01/2019 8:45	1803.261
1/01/2019 9:00	1803.282

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What is the easiest way to do this?

 

[steve the fish]

You could use a SUMIFS

=SUMIFS(B:B,A:A,"<="&C1,A:A,">"&C1-1/48)