Ticks are not pointing in when using plot_ts

[lindsayplatt]

This particular example produces ticks that are not pointing in when they should be. The second example does it correctly.

# does not work
xdat <- seq(as.Date("2010-10-01"), as.Date("2010-11-01"), by="days")
ydat <- seq_along(xdat)
plot_ts(xdat, ydat)

# works
xdat <- seq(as.Date("2010-10-01"), as.Date("2012-10-01"), by="days")
ydat <- seq_along(xdat)
plot_ts(xdat, ydat)