In B1:
=TIME(0,0,A1)
fill down.

Or the brutal way if you can't spare the B column: Enter
86400
in an empty cell (=the amount of seconds in a day, if you include the
night). Copy that cell. Select your A cells. Go menu Edit Paste special,
check Divide, OK. Format the cells as time.

HTH. Best wishes Harald

"bourbon84" skrev i melding
...
I have a column of numbers, ranging from 0 to 4000 seconds; A1 is 0, A2 is
1,
A3 is 2, etc. How do I convert that column to represent time, where 0
seconds
is 00:00:00, 1 second is 00:00:01, 2 seconds is 00:00:02, and 60 seconds
is
00:01:00, etc.? Thanks.