[R] How to specify year-month-day for a plot

[Gregory Coats]

Starting with year-month-day, for the variable gallons, I can easily plot the variable gallons, while disregarding the date. 
gallons <- c (15.973, 18.832, 17.392, 14.774, 19.248, 14.913, 15.226, 14.338, 18.777, 19.652)
plot (gallons, type="l", xlab="X label", ylab="Y label", col="blue”)

How do I direct R to plot the variable gallons, at the appropriate, irregularly-spaced places on the X axis, while paying attention to the year-month-day?

format = "%Y-%m-%d”
2020-01-05 15.973
2020-02-15 18.832
2020-03-10 17.392
2020-05-04 14.774
2020-06-21 19.248
2020-08-01 14.913
2020-08-27 15.226
2020-09-28 14.338
2020-11-09 18.777
2020-12-11 19.652
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