Partitioning by month causing an error?

I have a partition per each month, like this:

CREATE TABLE mmd_yr2019_3 PARTITION OF mmd FOR VALUES FROM ('2019-03-01')
TO ('2019-03-31');
CREATE TABLE mmd_yr2019_4 PARTITION OF mmd FOR VALUES FROM ('2019-04-01')
TO ('2019-04-30');

This breaks for dates at the end of the month. What's the better way to
write the bounds? 3/1 to 4/1 and then 4/1 to 5/1? Does that cause some
overlap issue?

Thanks.

--
Wells Oliver
wells(dot)oliver(at)gmail(dot)com <wellsoliver(at)gmail(dot)com>