Axes - R Graphics - page 265

Figure 8-39. Line graph with date format specified
Common date format options are shown in Table 8-1 . They are to be put in a string that is passed
to date_format() , and the format specifiers will be replaced with the appropriate values. For
example, if you use "%B %d, %Y" , it will result in labels like “June 01, 1992”.