555 timer to work once per day for 30 minutes
It's not easy to keep "time of day", even with a crystal-controlled timer. A 555 might be good to 1% (after adjustment) so it could gain or lose maybe 15 minutes per day. I might add that adjusting would be a monstrous PITA if you tried to use a 555 directly (and it's not that easy to get times like that out of 555- big expensive low leak capacitors and high value resistors). With a counter, you could use a much faster clock (say 1Hz), but the accuracy may still be a problem (see below). 

A crystal running a microcontroller would be much better, maybe seconds or minutes per month, or a really good crystal oscillator might keep within a couple seconds a year. 

If you really mean "approximately once every 24 hours" rather than at almost the same time every day then it is easier. In this case the time might be 9:00 AM one day, 9:14 the next day, 9:35 the next day etc. (the errors are cumulative).