Create a "date" class variable composed of your MONTH and DAY variables for plotting purposes, see this example with made-up data
library(tidyverse)
library(lubridate)
library(scales)
sample_df <- data.frame(
month = rep(1:6, each = 30),
day = rep(1:30, 6),
so2 = rnorm(180)
)
sample_df %>%
mutate(date = ymd(paste("2021", month, day, sep = "-"))) %>%
drop_na() %>%
ggplot(aes(x = date, y = so2)) +
geom_point() +
scale_x_date(date_breaks = "10 days",
labels = label_date_short(format = c(NA, "%B", "%d", "%H:%M")),
expand = c(0.005,0.005))
#> Warning: 2 failed to parse.
Created on 2021-05-17 by the reprex package (v2.0.0)
If you need more specific help, please provide a proper REPRoducible EXample (reprex) illustrating your issue.