R help - Dec 2004 - time data

I have a data set with date, time and rainfall (sample below)

my questions are (a) is there a command like as.date for time? and (b) 
Can R smooth data 6 hourly with such unevenly spaced data?

Thanks

Carla

09/29/02	 19:33	0
09/29/02	 19:34	0
09/29/02	 19:35	0
09/29/02	 19:36	0.1
09/29/02	 19:37	0
09/29/02	 19:38	0
09/29/02	 19:39	0
09/29/02	 19:40	0.1
09/29/02	 19:41	0
09/29/02	 19:42	0
09/30/02	 00:00	0
09/30/02	 01:50	0.1
09/30/02	 02:20	0.1
09/30/02	 02:40	0.2
09/30/02	 02:50	0.4
09/30/02	 05:00	0.7

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