I've tried a make check between make && make install. This fails because

difftime(
    as.POSIXct(c("1970-01-01 00:00:00", "1970-01-01 12:00:00"), tz="EST5EDT"),
    as.POSIXct(c("1970-01-01 00:00:00", "1970-01-01 00:00:00"), tz="UTC"))
## Time differences in hours
## [1]  5 16

returns a wrong result (should be [1] 5 17).

This problem has been reported long ago at https://bugs.r-project.org/bugzilla/show_bug.cgi?id=16843 and I've just verified that the issue persists even with latest Alpine 3.12.0. help(timezones) is pretty comprehensive and talks about the possibility of using R's internal zoneinfo database.

If the Dockerfile would

1. configure --with-internal-tzcode
2. set ENV TZ=UTC (which is used in plain Alpine Linux anyway) to suppress R's warning "system timezone name is unknown: set environment variable TZ".

time zone computations would be correct but the R installation would grow in size: share/zoneinfo has 2.4 MB.
Other ideas?