As timespan units span a variety of bases (1000 below seconds, 60 for second and minutes, 24 for hours, and 7 for days), the range of the input data determines the base used for calculating breaks
breaks_timespan(unit = c("secs", "mins", "hours", "days", "weeks"), n = 5)
demo_timespan(seq(0, 100), breaks = breaks_timespan())
#> scale_x_continuous(breaks = breaks_timespan())