hist of dates

Hi all

I wish to draw an histogram... with dates but the following append, i don't know where is the problem, help(hist.Date) works and i don't see any usefull information on what i'm doing wrong...

hist.Date(dt_cycles)

Error: couldn't find function "hist.Date"

hist.date(dt_cycles)

Error: couldn't find function "hist.date"

cycles

[1]  7  1  2  5 14  5

dt_cycles

dates_releves cycles
1    2005-07-01      7
2    2005-07-04      1
3    2005-07-06      2
4    2005-07-11      5
5    2005-07-25     14
6    2005-07-27      5

dates_releves<-as.Date(dates_releves)
hist(dates_releves,cycles)

Error in hist.Date(dates_releves, cycles) :
        invalid specification of 'breaks'

hist(dates_releves~cycles)

Error in hist.default(dates_releves ~ cycles) :
        'x' must be numeric

Any ideas would be great...
thks
guillaume.