Importing dates from SQL to R

Question

I'm trying to exploit the wild fires data set from kaggle (https://www.kaggle.com/rtatman/188-million-us-wildfires). Specifically I want to use the "DISCOVERY_DATE" variable, and other date variables but I cannot manage to keep them as date format when I import them into R.

I'm using DBI and RSQLite to read the data.

library(DBI)
library(RSQLite)
library(dplyr)
rep <- "data/"
con <- dbConnect(drv=RSQLite::SQLite(), 
                 dbname=paste0(rep,"FPA_FOD_20170508.sqlite"))

fires <- dbReadTable(con, "Fires")
head(select(fires,DISCOVERY_DATE))

  DISCOVERY_DATE
1        2453404
2        2453138
3        2453157
4        2453185
5        2453185
6        2453187

I don't know how to convert this into a date format either. I have tried as.Date(x) but it looks like I would have to guess the origin. I don't see any arguments allowing one to specify columns types in the dbReadTable function either. Is there a method, preferably using these libraries, to handle date formats upong reading the data?

Now amidst the many related questions, the following seems to correspond to my problem but it has no answer. dbReadTable coercing date column from SQL database to character

Thanks in advance.