Format before and after arguments for API query
Examples
# convert to epoch timestamp
seltime_fun(Sys.Date())
#> [1] 1752537600
# back to original
as.POSIXct(seltime_fun(Sys.Date(), before = FALSE), tz = Sys.timezone(), origin = '1970-01-01')
#> [1] "2025-07-15 23:59:59 UTC"