Problems creating a 24/7 calendar

I'm having a problem when creating a 24/7 calendar.
I login to the admin / system page and view the default calendar. I click the create new option and call my new calendar PCS247.
I ctrl select all columns (S thr to S) and untick the Mark as non working days.
At this point all the hahed out days (Sat / Sun) lose their hash as expected and when I click SAVE all is ok.
However If I then select a column such as M and set Start time to 00:00 and End Time to 23:59 ... when I click save all those day in the column switch to a non working Day (Hashed)
If I set the time to start at 01:00 and end at 23:59 .. then the above doesn't happen.

So I have two questions :
1) Why can I not set a working day from 00:00 to 23:59
2) If I could set 00:00 to 23.59 I still don't get a true 24hr day. It's only going to Miss a minute, but for a 24hr clock it's going to affect all sorts of KPI's. I did try to set 00:00:00 to 23...

OriginalPostID-256166