Calculating the difference between time stamps

I've got a spreadsheet of samples taken at certain time intervals for a period of 2.5 hours, they were collected in hh:mm:ss format. Most of them are approximately 5 minutes apart. What I'd like to do is convert the first time to 00:00:00 and then recalculate each sample from there. Is there an easy way to do this?

So, what looks like this right now:
8:45:00
8:45:36
8:50:36
8:55:36
9:00:36

Would look like this:
00:00:00
00:00:36
00:05:36
00:10:36
00:15:36
etc...

Thank you!

Type 08:45 into a random cell, then copy.

Highlight the cells you wish to amend, right-click, paste special, and select 'subtract'.

See, this is why I turn to the experts. I knew the concept but had no idea how to get there (and figured it would be just that easy...)

Thanks so much!

Like this??

Formula:

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Where your list begins in A1 (i.e. 8:45:00)

Beaten to it... I started in B2, by the way.