How to count how many days passed from the beginning

How to count how many days passed from the beginning

I'm working with daily schedule. Due to it is daily it doesn't consist any
information about DATEs, and looks like next:
"19:16:00"
"21:21:00"
"22:45:00"
"00:51:00"
"01:48:00"
"02:28:00"
"02:55:00"
"03:15:00"
"07:57:00"
"09:06:00"
"10:41:00"
"12:36:00"
"13:42:00"
"14:21:00"
"17:45:00"
"18:10:00"
"20:41:00"
"00:47:00"
"05:35:00"
"08:52:00"
"10:02:00"
Where first row is start, and last is finish. I need somehow by using
MYSQL only return days quantity which passed from beginning. For instance,
I expect to get next response.
"19:16:00" => 0
"03:15:00" => 1
"08:52:00" => 2
Thanks for any help.