You want to use dates on an axis.

Map a column of class Date to the x- or y-axis. We’ll use the economics data set for this example:

# Look at the structure
str(economics)

'data.frame':   478 obs. of  6 variables:
 $ date    : Date, format: "1967-06-30" "1967-07-31" ...
 $ pce     : num  508 511 517 513 518 ...
 $ pop     : int  198712 198911 199113 199311 199498 199657 199808 199920 ...
 $ psavert : num  9.8 9.8 9 9.8 9.7 9.4 9 9.5 8.9 9.6 ...
 $ uempmed : num  4.5 4.7 4.6 4.9 4.7 4.8 5.1 4.5 4.1 4.6 ...
 $ unemploy: int  2944 2945 2958 3143 3066 3018 2878 3001 2877 2709 ...

The column date is an object of class Date, and mapping it to x will produce the result shown in Figure 8-37: