Editing time that has its colon removed

[rhhince]

I have a large CSV file that has the time column stripped of its colon
meant to distinguish hours and minutes.

ie. 9:20 is displayed 9200.
23:55 is displayed as 2355

Is there a way of adding a colon automatically in the right spot? I
have over 875000 of these to do.

 

[Rick Rothstein]

Question... given how 9:20 is changed to 9200, what would 1:20 and 12:00
(and, depending on how you show it, maybe 0:12 as well) be changed to?