converting times to 15 min bands

[greyscale]

Hi, I have hundreds of rows of data of timestamped entries, I want to create a pivot table that will bring back the number of entries in 15 min bands (where it is always rounded down to the previous 15 min band). I presume I will have to create an extra column in the data before bringing it into the pivot table. e.g. the times on the left column below would be converted to the column on the right. Can anyone suggest how I might convert them?
16:12 16:00
13:39 13:30
13:46 13:45
13:46 13:45
10:01 10:00
15:08 15:00
14:56 14:45
14:51 14:45
16:33 16:30
10:43 10:30
13:54 13:45

I hope that makes sense. Thanks in advance.

[optomyst]

You can convert the data via the text to columns.. then set your formulas... make sense?

[6StringJazzer]

This formula will round down to the next 15-minute boundary, giving you your second column:

=A1-MOD(A1,(15/1440))

[greyscale]

Perfect! Thanks 6stringjazzer

[Haseeb Avarakkan]

Try,

=FLOOR(A1,"00:15")

[greyscale]

That works too, thanks Haseeb

[6StringJazzer]

I like Haseeb A's better than mine I was not thinking about FLOOR and did it the hard way.