Filter function help

Hello.. I have a few spreadsheet with time stamped log data spanning several months. The first column is the date formatted like "30/06/2013" and the second column is the time formatted like "00:02:30.576" (HH:MM:SS.MS)

The log is in 10 second chunks, but not aligned, so not repeatable timestamps. I need to filter the entire sheet to find the first sample of every day... Thought I could set the filter to 00:00, but because of how the log sample work, end up with multiple hits per day. Not sure how to test for the change of date, and how to get it to find the first change from the cell above.

have 5 files with 100 (ish) days, so couls do manually if needed, but thought I'd ask if anyone had a simple way to automate??

Have attached small sample of one of the files for reference..

Thanks Chris